The cost of control is extremely important in terms of its impact on what is “practical” in the world of production.  Even in medical, military and aerospace systems where cost is often a secondary consideration, the actual cost and performance of a new process or piece of equipment has to be gauged against the benefit that it will produce.  If the benefit is greater in value than the cost, then funds and effort need to be committed to the new project.

There are significant trends in the marketplace that are constantly changing the cost of control.  As we look at the mechatronic arena in particular, recent increasing cost trends for copper wire, lamination steel and permanent magnets have been pushing prices up steadily in the range of 5-6% per year.  This situation is expected to continue.

Recent threats from China about restricting export levels for Neodymium magnets have made magnet pricing very speculative, read high as a kite.  However, Molycorp and others around the world are bringing Neodymium ore into the market and companies like Arnold Magnetics are gearing up to provide finished products without the use of Chinese sourced material.  Good new to those in the motor sector.

On the control side of mechatronics, the power Fet has dropped in cost by 50% in recent years and costs are expected to continue to decline following the traditional cost performance over time that is characteristic of the semiconductor industry.  Add to this the incredible cost performance improvement in embedded microcontrollers used in motor control circuits and you have even more good news for the mechatronic suppliers.

Bandwidth for these controllers now provides motor control that operates in the sub-microsecond range with efficient instruction sets and pre-configured PWM macros to make code creation more efficient.  Typical pricing for these processors is well under $5 making them ideal for a wide range of applications in industry and commercial white goods.  The marriage of low cost motor control cores and reduced cost power electronics should signal declining prices for motor controls for the mid- to high performance applications.  This cost improvement should more than offset the price increases expected in the cost of electrically controlled motors.

Some families of processor have native CAN or Ethernet communications interfaces with multi-threading software to guarantee that high priority instructions in the motor control code will not be impacted by messaging from outside applications.  Network technology is providing fast, and in some cases, deterministic forms of Ethernet like EtherCat making the servo network the control architecture.   This approach to the network demands of high performance control reflects a general shift to low cost, high reliability platforms that are ready to transform the controls landscape in the mechatronic arena.

It’s an interesting time to be in the controls business.

Mechatronic Tips

Clean rooms are classified according to the number and size of the particles permitted per volume of air. For example, a Class 10 clean room denotes that no more than ten particles of 0.5 µm or larger and zero particles of 5.0 or larger are permitted per square foot of air. Contaminants come from people, process, facilities, and equipment. In order to control contaminants that are invisible to the human eye, the manufacturing cell and in many cases the entire room must be controlled. Robots used in this environment must meet stringent clean room certification requirements to prevent them for acting as a source of contamination.

Much of the hardware used in a clean room robot is the same as any other robot with the important exception of a combination of sealed covers to prevent particles from escaping the robot, stainless steel hardware, proper non-gassing lubricants and vacuum to evacuate any internally generated particles. Robots for clean room processes have special considerations for harnesses, . . . “which can be a serious particulate generator and a major design challenge for clean applications,” said Scott Klimczak president of CHAD Industries, a pioneer in the area of wafer and substrate handling WLP I (Wafer Level Packaging) applications.

As a matter of practice, materials prone to particle generation are substituted or coated to eliminate the potential for contamination.

Certification is done by counting the number of particles generated when the robot is in motion. For this process the industry uses particle counters that are calibrated to meet or exceed the standards set by NIST (National Institute of Standards and Technology). In addition to NIST traceable practices, other standards of particle counter calibration include Japanese Industrial Standard (JIS) B 9921, Light Scattering Automatic Particle Counter, and ASTM F 328-98, Standard Practice for Calibration of an Airborne Particle Counter Using Monodisperse Particles. Adept Technology, Inc. a leading manufacturer of clean room robots tests robots both internally and through third party testing and certification to ensure integrators and end-users deploy their equipment appropriately to meet manufacturing cleanliness requirements.

There are two accepted clean room specifications, the ISO 14644-1 spec and the Fed 209E spec.

Depending on the cell design and the robot style selected, a lower class robot may be used and still meet the overall system requirements if the system is designed appropriately. For example, for a semiconductor wafer application, if a robot can operate under the wafer with a vertical laminar flow of clean air present sweeping the particles away from the product, the ultimate requirement for the robot may be less stringent.

Installing the clean room robot requires attention to cleanliness. “Robots built for Class 1 environments are wrapped in several layers to protect them as they are shipped to the site,” said Kevin Lonie, application sales manager for Clear Automation, a Connecticut based automation integrator specializing in the design, engineering, fabrication and installation of integrated robotic and machine vision systems. “Then at the site the equipment is moved through progressively cleaner spaces as the wrapping is wiped down and finally removed before entering its ultimate clean room destination.”

Once wiped down with clean room wipes to remove any foreign particles, it is a good practice to connect the robot to the plant’s vacuum system and evacuate the robot for several hours to make sure all particles are purged completely.

www.adept.com

Mechatronic Tips

The lab-tested material responds to almost the same pressures as human skin and with the same speed, they reported in the British journal Nature Materials.

Important hurdles remain but the exploit is an advance towards replacing today’s clumsy robots and artificial arms with smarter, touch-sensitive upgrades, they believe.

The “e-skin” made by Javey’s team comprises a matrix of nanowires made of germanium and silicon rolled onto a sticky polyimide film.

The team then laid nano-scale transistors on top, followed by a flexible, pressure-sensitive rubber. The prototype, measuring 49 square centimetres (7.6 square inches), can detect pressure ranging from 0 to 15 kilopascals, comparable to the force used for such daily activities as typing on a keyboard or holding an object.

A different approach was taken by a team led by Zhenan Bao, a Chinese-born associate professor at Stanford University in California who has gained a reputation as one of the top women chemists in the United States.

Their approach was to use a rubber film that changes thickness due to pressure, and employs capacitors, integrated into the material, to measure the difference. It cannot be stretched, though.

The achievements are “important milestones” in artificial intelligence, commented John Boland, a nanoscientist at Trinity College Dublin, Ireland, who hailed in particular the use of low-cost processing components.

In the search to substitute the human senses with electronics, good substitutes now exist for sight and sound, but lag for smell and taste.

Touch, though, is widely acknowledged to be the biggest obstacle.

Even routine daily actions, such as brushing one’s teeth, turning the pages of a newspaper or dressing a small child would easily defeat today’s robots.

Bao added important caveats about the challenges ahead.

One is about improving the new sensors. They respond to constant pressure, whereas in human skin more complex sensations are possible.

This is because the pressure-sensing cells in the skin can send different frequencies of signal — for instance, when we feel something painful or sharp, the frequency increases, alerting us to the threat.

In addition, Bao warned, “connecting the artificial skin with the human nerve system will be a very challenging task”.

“Ultimately, in the very distant future, we would like to make a skin which performs really like human skin and to be able to connect it to nerve cells on the arm and thus restore sensation.

“Initially, the prototype that we envision would be more like a handheld device, or maybe a device that connects to other parts of the body that have skin sensation.

“The device would generate a pulse that would stimulate other parts of the skin, giving the kind of signal ‘my (artificial) hand is touching something’, for instance.”

In the future, artificial skin could be studded with sensors that respond to chemicals, biological agents, temperature, humidity, radioactivity or pollutants.

berkeley.edu



Mechatronic Tips

The robot unit, known as Robolink, was primarily designed for robot developers and laboratories that work with humanoid systems, as well as with lightweight engineering systems for handling and automation. The design was inspired by Dr. Rudolf Bannasch, Managing Director at the Berlin-based company EvoLogics, a high-tech company working in the field of bionics and humanoid robots. He provided both the motivation and developmental support behind this Robolink component.

It consists of a drive-and-control unit, joints in different lengths, and arms in different sizes, including a duct for additional control cables. The jointed arms are made from carbon fiber reinforced plastic and other lightweight materials. At the end of the jointed system is the option to connect to different types of tools.

The drive-and-control unit was purposely designed as a black box. Robot developers have the option to work with pneumatics, electro technology, or hydraulics.

The bionic core of the robot’s skeletal parts is the injection-molded plastic joints. They are controlled through cable pulls that transfer tensile forces, similar to the way tendons function in humans. The cable sheath is held and the inner cable moved. This way, the gripper, shovel, hook—or whichever tool the developer chooses—is moved and operated.

All data cables are routed safely through the jointed arms. The cable pulls are routed through from one joint to the next—just as joints are connected in humans. Only four cables are required for each plastic joint to rotate and swivel freely. These cables convey images, acoustics and forces, which are the artificial senses of humanoid robots.

The cables themselves are made from technical synthetic fibers. The fibers are extremely strong, hardly stretch at all, are resistant to chemicals, and are lubrication-free and wear resistant. When compared to steel, their lighter weight also makes them much more energy efficient.

Since the system is modular, it can be constructed with all kinds of humanoid robot configurations. This ranges from jointed arms, moving ‘digger’ arms, through to four-legged ‘creatures.’ The joints can be easily combined as required.

igus’ development objective was to keep the moving mass as low as possible, so that the actuators can be separated from functioning tools, such as grippers, hands, suction cups, and so on. Particular attention was given to enable quick assembly, as well as the use of tribo-optimized plastics to reduce lubrication needs and weight.

igus
www.igus.com

Mechatronic Tips

Different drive principles are used, depending on the application: Hexapods with NEXLINE® drives make a positioning system that is vacuum compatible and non-magnetic.

These Hexapod systems include a controller that lets you set a pivot point anywhere inside or outside the Hexapod working space. The freely definable pivot point stays with the platform, no matter how it moves. Moves are specified in Cartesian coordinates and the PC-based controller transforms them into the required motion-vectors for the individual actuator drives.

The miniature hexapod system delivers more than 10 lb of force and motion in all six degrees of freedom.  This 6-axis robot can be used for manufacturing and part placement that requires high precision for microscopy applications or laser and optical alignment. Its size is 10 cm in diameter and 11.8 cm in height. Minimum incremental motion is 0.2 microns (40 nm resolution). Travel ranges to 40 mm linear and 60° (rotation). Velocity is 10 mm/s.

PI (Physik Instrumente)

www.pi-usa.us

Mechatronic Tips

After two decades of experience with the design and production of hexapod robots, PI’s electro-mechanical / piezoelectric six-axis positioners are among the most advanced multiaxis precision motion control systems in the world.

Features and Advantages of the M-810 Miniature Hexapod

• Operation in Any Orientation
• High-Stiffness 6-Axis Hexapod with 5 kg Load Capacity
• Very Compact: 10 cm Diameter, 11.8 cm Height
• 0.2 Micron Minimum Incremental Motion (40 nm Resolution)
• Long Travel Ranges to 40 mm (linear) and 60° (rotation)
• Powerful Controller with Freely Definable Virtual Pivot Point
• High Velocity of 10 mm/s
• Linear and Rotary Multi-Axis Scans

Parallel Kinematics Advantages
Parallel-kinematic motion systems have a number of advantages over standard serial kinematic (stacked) positioning systems:

Virtual Pivot Point: Rotation Around any Point, not unlike the Human Hand
Only one Moving Platform, No Accumulation of Guiding and Lever-Arm Errors
No Moving Cables for Improved Reliability and Precision
Smaller Package Size
Increased Stiffness, Reduced Inertia, Better Dynamics

Smaller Motors and Encoders, Controller & Software Included. The limited space necessitated the usage of new  technologies for encoders, motors and other integrated electronic components.  The M-810 is compatible with PI’s tried and proven hexapod controllers that are supported by windows software and a library of drivers and programming examples for applications such as optical alignment etc.  PI also provides simulation tools for hexapod integration.

PI Hexapods come with load ranges from 2 kg to >1000 kg.

Applications

Precision manufacturing, high precision placement of parts; alignment of optical components & lasers, microscopy applications, neuroscience.

www.physikinstrumente.com

Mechatronic Tips

Invasive bladder cancer has a very high mortality rate and generally results in death if not treated. During a radical cystectomy, the entire bladder (and prostate, if the patient is male) is removed. According to Laungani, performing this robotically allows for a minimally invasive approach. The advantages include less blood loss, less pain, and quicker recovery. Just as importantly, it provides comparable rates of cancer cure as compared to more traditional surgery.

In 2004, Saint Joseph’s Hospital in Atlanta was designated as the exclusive training center in the Southeastern United States (Georgia, Alabama, Florida, South Carolina and Mississippi) for robotic surgical systems. Since that time, Saint Joseph’s has become the world-wide site for surgeons to train on robotics.

www.stjosephsatlanta.org

Mechatronic Tips

Many electro-mechanical systems can qualify as mechatronic systems. Don’t agree? Take a look at these application examples that demonstrate both the power and potential of mechatronics in action.

Complete subsystem medical tables use mechatronics systems for precise multi-axis positioning.

Mechatronics integrates mechanical and electronic technologies with application-specific software to perform a particular task. Engineers who use mechatronic components and systems do so to focus on:
• improving precision, repetition, and flexibility in movement;
• saving energy;
• expanding function;
• reducing system size, weight, and footprint;
• and minimizing both the physical and audible environmental impact.
Mechatronic designs can be as elementary as “building block” components or as sophisticated as fully integrated systems. The basic building blocks are represented by individual components, such as linear bearings and guides, bearings integrated with sensors, or ball and roller screws.  You can specify these components individually in an application to help control movement, reduce friction, create a mechanism for driving linear motion, and even provide feedback on how fast equipment is rotating and in what position.

The next level combines components into a sub-system that serves as a self-contained unit to deliver more in terms of speed, strength, accuracy, reliability, or other measurement compared with basic building block components. Depending on application needs, sub-systems can include feedback devices to ascertain position or special configurations that can support structural loading. Some sub-systems will accommodate unique operating conditions while others fit more universal specifications.

Beyond sub-systems, fully integrated mechatronic systems offer “complete package” approaches that independently respond to inputs and offer real-time feedback and actions.  For example, an electric parking brake engineered as a mechatronic system can receive specific input about the
current operating condition from a CANbus network. In effect, the brake “knows” when it should activate or release, based upon programming in the integrated actuator specific to that vehicle.

Our applications casebook describes a range of examples demonstrating both the power and potential of mechatronics in action.

Modular actuation systems for patient beds convey precise, safe, secure, and reliable power-driven adjustment and positioning.

Linear ball bearings in stretcher-mounting system
Space is scarce inside ambulances, so placing and securing a stretcher can become an issue.  One mechatronic approach is to use linear ball bearings to guide the horizontal movement of a stretcher in and out of the ambulance.

The benefits here include high load-carrying capacity (to accommodate all sizes of patients), robustness and reliability, and the delivery of smooth, low-friction movement (greatly assisting EMTs).  In addition, the patient bed remains tightly secured during the ride in the ambulance.

Actuators onboard “factory on wheels”
In agricultural harvesting, the combine essentially serves as a “factory on wheels.”  Raw material is brought into this “factory” (harvested with the header) and proceeds through the machine where the crop (such as wheat) is separated from the chaff (waste) by the threshing mechanism.  The grain from the wheat passes over a sieve mechanism where it is sifted out of the waste and collected.  The chaff can then be reprocessed for complete threshing and then ejected from the rear of the combine.

Each of these processes requires movement. Since there is only one source of power (the engine), how and where to deliver that power is critical to machine function.  The prerequisite for any component is that it must be mechanically robust and able to survive in the dirty and dusty environment usually encountered.

Traditional components used to perform the necessary functions include belts, chains, or hydraulics.  Each presents its own challenges in delivering power to each point.  Applying tailored actuators for some operations, such as the threshing mechanism, cleansing fan, secondary separation system, sieve table, and auger, can improve the overall efficiency and reliability of the machine.

Electro-hydraulic steering system for off-road vehicles
Some applications can benefit from a combination of technologies, mechatronics and otherwise.  Electric steering offers flexibility and hydraulics delivers the necessary power density.  Combined, the two parts replace the traditional steering column with a more ergonomic design; reduce the number of parts; simplify assembly procedures and processes; and use less space.  Without the steering column operators experience less noise, better safety, and avoid hydraulic leaks in the cab.

One example of a closed-loop system integrates: a mechanical/electronic (mechatronic) steering module; a controller regulating all steering functions; high resolution kingpin bearing sensors for steering position input and actual steered wheel feedback; and an electrically actuated proportional valve.  Each component “talks” to the next using CANbus protocols.

When the operator turns the wheel, a signal travels to the controller with data indicating the angle of the turn and the desired position of the wheels.  The controller takes the signal and commands the proportioning valve to actuate the hydraulic cylinder, which forces the steered wheels to move to the desired position.  The position sensor integrated into the kingpin measures the position of the steered wheels and returns feedback data to the controller, which are compared to the desired position input to correct any discrepancies.

This system can be programmed to adjust the number of turns for the steering wheel from lock-to-lock.  Programming software governs steering sensitivity changes through vehicle speed.  This feature is especially useful in operating off-road vehicles, where it is often necessary to steer quickly at lower speeds and slowly at higher speeds.

Depending on the vehicle requirements, steer-by-wire modules with a constant, non-programmable torque may be preferred.  These plug-and-play systems send an electronic signal on the speed, acceleration, and direction of the steering wheel movement; and can increase cabin design flexibility and enhance operator ergonomics.

Mast height control units monitor the mast location as it travels up or down.

Mast height control unit for forklifts
A mechatronic system can automatically position the mast on industrial vehicles, such as forklifts.  Integrated sensor bearings detect mast height and convey rotational speed and direction feedback from the ac motor.

Accurate mast height control is important when forklifts quickly move from place to place, placing or retrieving pallets or containers to and from bin locations. Through a simple readout of the mast’s height compared to a pre-programmed shelf height, sensor bearings on the mast will automatically position it to the desired height with the push of the button or the flip of a switch.

The control unit mounts on the mast to monitor its location as it travels up or down and sends a continuous signal to the controller.  These signals are interpreted into precise measurements.  Using either a pre-programmed mast height system or a simple digital readout system, the vehicle “knows” the height of the load and can trigger other safety systems.

For example, the forklift’s safety controls can be programmed to limit speed or turning radius, depending on the height of the load, reducing the possibility of the vehicle tipping over.

Alternatively, the safety system can prevent the mast from rising beyond a specified height when the load exceeds a predetermined weight.

Two different designs have been created for mast control units.  A spring-loaded cam arrangement uses spring force to press the sensor bearing against the mast.  This unit is driven directly by the moving frame of the mast.  Pulley arrangement units are driven by either a wire or belt incorporated into the design of the mast-positioning system.

Both the cam and pulley control units respond directly to a designer’s need for smaller components, simpler assembly, and reliable performance.

An electro-hydraulic steering system for off-road vehicles combines mechatronics and hydraulics systems as shown in this diagram.

Surgical and patient tables
Surgical equipment must meet stringent hygiene standards and perform reliably and consistently.  In medical applications, electro-mechanical actuation systems have distinct advantages over conventional hydraulics.  Without hydraulic fluids, there are no leaks to contaminate operating or patient rooms. The usually quiet electro-mechanical systems foster a lower stress environment for patients.

Electro-mechanical systems move telescopic pillars, or lifting columns, on surgical tables quickly and silently.  For structural support, rigid aluminum profiles and precision glide pads in the columns lift offset loads without deflection.  Combinations of screws and gears feature high push force capabilities and low noise levels.  Telescopic pillars can satisfy other applications, including patient-positioning tables for medical imaging, treatment, and ophthalmic examination, among others that require vertical action and structural support.

As part of the system, guiding actuators extend or retract the telescopic pillars.  Columns can run quietly and with minimal vibration at maximum speeds up to 45 mm/sec, depending on the model.  Stroke lengths can be up to 700 mm.

Control boxes synchronize and control multiple actuators for a flexible system.  The proper combination of control boxes and actuators ensure component compatibility and help reduce time spent in design, production, and assembly.

Interest among OEMs for fully integrated medical equipment systems has led to the design and development of subsystem medical tables.  In one application example, these tables (one is mobile and the other is “fixed”) are incorporated into machines for urology.  Through mechatronics components for multi-axis positioning, doctors can precisely, easily, and comfortably move patients for specific treatment.

Patient beds
Mechatronics has found a home in hospital rooms and in similar patient-care settings. Modular, power-driven actuation systems let caregivers precisely, safely, and securely adjust and position patient beds.  Other applications include couches, stretchers, and physiotherapy and examination tables in various healthcare settings.  Specialized actuators, recliners, and control units integrate
easily into standard bed platforms.

Beds equipped with such actuation systems can offer variable height adjustment; an adjustable backrest with CPR function; special positioning with auto-contour for comfortable sitting; and adjustable elevation of legs and knee-fold.  Full electrical control comes from handsets, bilateral pedals, and selective function limiters.  A manual quick-release mechanism safeguards in case of emergency.

Final Note: Regardless of application, an understanding of particular requirements and the operating environment will help guide your choices.  Partnering early in the design stage with a knowledgeable engineering resource can help identify the best components or systems for the job.

SKF USA
www.skfusa.com

Contact Mark D. Hinckley at 267-436-6510 or email Mark.D.Hinckley@SKF.com

Mechatronic Tips

“Advanced Robotic Techniques – da Vinci Surgical System” will take place at Stamford Hospital’s Whittingham Pavilion, Rooms 1 and 2 on Sept. 14 from 1 – 3 p.m. At the presentation, two hospital surgeons will demonstrate how the da Vinci works and appropriate surgical procedures for the system. Additionally, the pair will explain the long list of benefits to the minimally invasive technology.

The free seminar will be led by Stamford Hospital’s Chairman of Obstetrics and Gynecology Dr. Lance Bruck and the Director of Stamford Hospital’s Department of Surgery’s robotics program in urology Dr. Ketan K. Badani.

Last year, Stamford Hospital unveiled the da Vinci Surgical System for complex urological and women’s health surgeries. With the da Vinci, the surgeon is at the controls of a sophisticated surgical robot to perform the most complex and delicate procedures. da Vinci offers unmatched precision with the ability to make small incisions through the aid of enhanced 3D optics.

An expert in minimally invasive procedures, Dr. Bruck enlists the aid of the da Vinci system at Stamford Hospital for numerous gynecological surgeries including hysterectomies. He previously developed the Minimally Invasive Surgery Fellowship at Jacobi Medical Center, where he was Vice Chairman of the Department of Obstetrics, Gynecology and Women’s Health. Dr. Bruck succeeded in raising the funds to support the Fellowship, primarily through industry support.

Dr. Ketan K. Badani is also the Director of Robotic Surgery at New York-Presbyterian Hospital/Columbia University, where he leads one of the largest and most comprehensive robotic and oncology programs in the country. He is one of only a few select surgeons in the world who have performed more than 1,000 robotic surgeries. In July, Dr. Badani began performing radical prostatectomies at Stamford Hospital with the da Vinci Surgical System.

Dr. Badani trained at the Vattikuti Urology Institute in Detroit, Mich. and is among the most experienced practitioners of robotic prostatectomies in the world. He is a noted author and lecturer and has published extensively on the subject, including landmark articles in the field of robotic surgery. Dr. Badani’s research in surgical technology continues to improve the quality of life for men after robotic surgery while maintaining the highest cancer cure rates.

Mechatronic Tips

The kidney, damaged by four tumors, was extracted through an incision of about three inches near the patient’s navel of a 50-year-old patient during a complex minimally invasive robotic procedure that lasted approximately 2.5 hours.

“We traditionally try to save the kidney for smaller tumors, performing a robotic partial nephrectomy”, says Dr. Rogers. “For larger tumors, however, patients would get a very large incision on their side. Now, we can remove kidneys with cancer through a single three- inch incision near the patient’s belly button.”

The potential benefits to performing the SIRS nephrectomy are improved cosmetics, quicker recovery times, less scarring and blood loss. Dr. Rogers and his colleagues have also pioneered robotic surgery for smaller kidney tumors, allowing them to perform a partial nephrectomy to remove tumors that might otherwise require total kidney removal or a large open incision. While these procedures are considered revolutionary because they preserve the healthy portion of the kidney and shorten recovery time, they are not practical for patients with large tumors.

Henry Ford doctors have performed more than 130 robotic kidney surgeries using four or five incisions of less than one inch. When Henry Ford doctors perform robotic surgery with the da Vinci system, a camera and small robotic instruments are inserted through small incisions and controlled by the surgeon from a nearby console machine.

In the SIRS procedure, Dr. Rogers inserts the robotic arms through a single incision near the belly button, and sits at a nearby machine controlling the robot throughout the operation.

“I control every movement made by the robotic arms,” says Dr. Rogers. “The robotic instruments are like having my hands inside the body.”

Working through the single small incision, the robot-assisted surgeon inflates the abdomen; moves the large intestine aside to reach the kidney; clips or ties off the vein and artery that take blood to and from the kidney; detaches the rest of the kidney, and removes it.

Kidney cancer is diagnosed in approximately 55,000 people a year and the most common treatment option is an open surgery with a large incision about a foot long. Surgeons sometimes must remove a rib, and they must go through muscle to remove the kidney. Recovery can be up to two months with a weeklong hospital stay.

This week’s innovative and successful kidney procedure comes after Henry Ford has established itself as the leading facility worldwide for robot-assisted surgical treatment of prostate cancer. More than 4,000 such procedures have been performed by Henry Ford surgeons since 2001.

Mechatronic Tips

A system-level approach moves robotic surgery from science fiction to reality.

By PJ Tanzillo
National Instruments

In 1981, Star Wars Episode V: The Empire Strikes Back featured a scene in which autonomous robotic surgeons attached a mechanical hand to Luke Skywalker after his climactic battle with Darth Vader. Real-life autonomous robotic surgeons are still just fiction, but a new breed of medical machines is taking advantage of robotic concepts to aide surgeons with complex medical procedures.

Combining sophisticated and reliable electronic control systems and high-level design software with advanced mechanical elements has improved procedural safety and patient comfort level.

The improved medical machines are the result of applying a mechatronics approach to merge mechanical, electrical, control system, and embedded software design. It represents an industry-wide effort to improve the design process by integrating the best-available development practices and technologies to streamline the design, prototype, and deployment stages. By using system-level design software, domain experts, scientists, and doctors, who have expertise in medical procedures but not necessarily in programming, can develop medical machines themselves. With this approach, they can reliably develop, test, and validate complex robotic control systems. This opens up a new class of safety-critical applications that were previously out of reach of computer technology.

The University of Nebraska Medical Center, OptiMedica, and Lebanese University have all developed surgical devices – the da Vinci Surgical System, the PASCAL Photocoagulator, and a photodynamic-therapy robot, respectively – that have benefited from a mechatronics approach to development.

The da Vinci Surgical System
Laparoscopy is a type of minimally invasive surgery that uses long instruments inserted through small incisions. Compared with traditional open procedures, laparoscopy has revolutionized the treatment of abdominal pathologies by shortening recovery time with less pain, fewer adhesions, and better postoperative quality of life.

However, manual laparoscopy has also revealed several limitations during operation, including lack of depth perception, poor camera control, limited degrees of freedom of the instrument tips, and inverted hand-instrument movements. These limitations lead to unnatural and painful surgical postures that result in surgeon fatigue.

The advent of robotic assistive surgery using the da Vinci Surgical System (dVSS) – from Intuitive Surgical, Inc., in Sunnyvale, CA – has overcome some of the limitations of manual laparoscopy. In robot–assisted laparoscopic surgery, the surgeon sits at a console and remotely controls instruments via a surgical robot (see Figure 1). The 3D visualization provides depth perception and increased dexterity.

The wrist-like articulations of the instruments in the console have also been shown to improve surgeons’ dexterity by diminished tremor, scaled motion, and increased range of motion. The coordinated hand-instrument movement reduced training time using robotic systems compared to manual laparoscopy. The dVSS has been approved by the FDA for gastrointestinal, thoracic, urological, gynecological, and cardiac procedures.

The Nebraska Biomechanics Core Facility in the HPER Biomechanics Laboratory at the University of Nebraska at Omaha and the Robotic Surgical Laboratory at the University of Nebraska Medical Center collaborated to develop a training program for robotic surgery in which new surgeons can learn how to use this advanced robotic technology.

Using LabVIEW software, they acquire all the information from the robotic surgical system by connecting with the dVSS via TCP/IP. To acquire physiological measurements such as muscle activations and joint angles from the surgeon, they use the NI USB-6009 data acquisition (DAQ) device to connect the electromyography system and electrogoniometers. With this system, instructors can objectively evaluate surgical proficiency before and after the robotic surgical training protocol.

In this training protocol, they also use LabVIEW to create visual real-time feedback to show trainees how much force they apply on the training task or animate tissue. This visual feedback helps the trainees reduce the tissue damage they inflict with the procedure.

The PASCAL Photocoagulator
Used by retinal surgeons to treat a number of eye conditions, laser photocoagulation involves the controlled destruction of the peripheral retina using targeted laser pulses. While this type of treatment has proven effective at reducing the chances of vision loss by as much as 50%, it can be very tedious to both patients and doctors. Ophthalmologists can deliver only one burn at a time, and treatment can require as many as 2,000 burns. A full course of treatment typically requires two to four sessions, each lasting 12 to 15 minutes.

LabVIEW is used to control the robotic arm responsible for extremely precise photodynamic therapy application for cancer patients.

With a small, three-member design team, OptiMedica developed the PASCAL (Pattern Scan Laser) Photocoagulator. PASCAL has a fully integrated pattern scanning laser system that provides significantly improved performance for the physician administering the treatment as well as an enhanced therapeutic experience for the patient.
OptiMedica used the LabVIEW FPGA Module and commercial off-the-shelf (COTS) hardware from National Instruments because it provides the hardware determinism and fast response times needed to deliver large batches of precisely placed laser pulses in a fraction of a second. This significantly reduced the number of patient office visits and increased the comfort of the procedure.

With a single graphical development platform, OptiMedica quickly and efficiently designed and prototyped the machine to demonstrate the system to potential investors. Then, it took advantage of the smooth migration path to deploy the final system on intelligent PCI DAQ hardware.

Photodynamic Therapy
When treating cancer, oncologists select from a number of techniques depending on the type and stage of the tumor in question. The most common techniques used today are photodynamic therapy (PDT), surgery, radiation therapy, chemotherapy, hormone therapy, and immunotherapy. PDT is a specialized form of phototherapy, a term comprising all treatments that use light to induce beneficial reactions in a patient’s body. PDT is a new technique capable of destroying unwanted tissue while sparing normal tissue.
During PDT treatment, a drug called a photosensitizer is administrated to the patient by injection. The photosensitizer alone is harmless and has no effect on either healthy or abnormal tissue. However, when light emitted by a laser is directed at the tissue containing the drug, the drug is activated and the tissue is rapidly destroyed precisely where the light has been directed. With this technique, oncologists can target the abnormal tissue with careful application of the light beam, which translates into more effective treatment.
Lebanese University developed an automated robotic mechanical manipulator with the primary function of skimming along the patient’s skin while performing the PDT technique. The robot uses NI motion controllers to precisely position the laser heads over the affected area of the patient’s body in certain geometrical designs, such as circular or elliptical shapes, to destroy the tumor.

The development team began by simplifying its robot configuration into 2D applications and by simulating movement using LabVIEW. Then, it extrapolated the same reasoning to a 3D problem and simulated the movement following the same process adopted in the simple 2D application. Finally, the team replaced the simulated input and output signals with measurements taken from real sensors and from driving real motors to control the real robot.

To learn more about designing and prototyping medical devices, visit http://www.ni.com embedded/medical_device.htm

National Instruments
http://www.ni.com

Mechatronic Tips

The motion is often powered with small stepping motors and a variety of mechanical solutions, some using timing belts and pulleys, some using lead screws, and some using rack and pinion acuation. It doesn’t look terribly difficult, but the fact is that as throughput demands increase, the motion is much more difficult. Components that are cantilevered tend to flex and oscillate which can disturb the accuracy of the motion or require settling time between motions.

There are no simple rules for the kinematics of these systems that will make them more efficient. Next generation throughput is going come with some R&D and increased hardware costs. And, next generation performance is going to require next generation design tools, which hopefully are on the near horizon.

The motion is not “mission critical” as it would be for a heart/lung machine or other system that involves risk to human life. So conventional controls are acceptable. But the emphasis of the equipment is the data that results from the processes. So a lot of care is taken to insure that the right data is associated with the right sample. A lot of money is spent on the PC software and hardware to make sure that the data is accurate.

The motion control aspect of this industry is not the primary focus of its engineering efforts. Some companies are already experiencing limits in what the hardware can do. So it remains, to get to the next performance plateau, we will need to throw out the handbook of how its been done up to now and start over with a clean sheet of paper.

As with most mechatronic applications, there has to be a change in the mechanical design of the system in order to achieve better throughput. What that change is, is not immediately obvious or someone would already be doing it. But that is how the progression takes place.

So we’ll stay involved in the industry and see how the next evolution takes place.

Mechatronic Tips