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Incredible Voyage - Using tried-and-true Servo Technology

18 Feb 2014
Scott Evans

Do you remember the 1966 movie Fantastic Voyage? What about Innerspace? Both of these movies feature stories about a small vessel working inside of the human body. At the time these movies seemed impossible because there were microscopic humans operating the ships.

Of course now it is 2014 and surely you've heard of Arthroscopy.

In my last blog post, I discussed drive-by-wire in a car. Essentially, the mechanical linkage between you and the steering wheel clutched in your white-knuckled fists is going away-replaced by sensors on the steering wheel that tell an actuator motor which way, how hard, and how far to turn the car's wheels based on how far and how hard you are turning the steering wheel.

Let's turn the concept inside out now. Suppose instead of wheels, a machine was holding surgical needle and thread. Or a camera. Or a scalpel. Or a stent.

Or all of them at once… …And all were inside your body.

And instead of you holding the wheel, a surgeon was holding the wheel. No mechanical linkage between the surgeon's hands and the scalpel.

Welcome to the 21st century. Over 2,000 hospitals have this type of machine, known as Surgical Robot or Surgical-Assist Robot.

Let's look first at Hansen Medical's Magellan Robotic Catheterization System. To steer the mechanism, the surgeon moves a joystick. The joystick is at the end of inertia arms, which introduce some resistance to the motion, not by way of friction but by way of inertia. The same way the mechanics of a car's steering wheel column might resist a quick "jerk" of the steering wheel.

What makes this robotic system so nifty, in terms of how it feels in the surgeon's hands, is its use of haptic technology: the system senses how much friction the patient's artery or cardiac wall introduces, as well as how fast the catheter is moving, then will provide force feedback to the surgeon through the inertia arms and joystick. This feedback, combined with the dashboard he is watching, tells the surgeon where he needs to go and how fast, while eliminating pain or contusions in the patient. This dramatically reduces time to operate, and mitigates pain and swelling in the patient.

In terms of Kollmorgen products, it could be said that the surgeon controls actuation through a coordinated motion controller and amplifier with a hypersensitive current transducer to an actuator such as a linear motor or screw actuator. The controller reads the current transducers and other sensors; When, say, the catheter touches the arterial wall, the controller commands the actuator in the opposite direction the surgeon is commanding, thus providing force feedback. All of this is happening in the Nm/µm scale; unlike the car, which is commanding on the cm/dm scale.

Intuitive Surgical Patient-Side CartIntuitive Surgical's Da Vinci minimally invasive Surgical System works similarly in that it allows the surgeon to work with greater precision. For the iron-stomached, there are many YouTube videos of these surgeries.

In both of these examples, the driver or surgeon instructs the tool, but is not actually touching the tool. The tool is driven robotically with highly reliable servo technology. And the sensors, used algorithmically to control the servo system, drive the same servo system in the opposite direction as the driver in order to provide haptic feedback to the Surgeon.

Can you think of any other classic movies where futuristic capabilities were portrayed that are now common place? How about innovations utilizing servo technologies? Stay tuned for my next post on incredible applications brought to you by motion control systems.

About the Author

Scott Evans

Scott Evans - Author
Scott has been with Kollmorgen for 7 years, currently as Director of Global Product Planning. Scott also has played the role of Business Unit Director for the Americas for Kollmorgen. Scott was founder of Advanced Digital, a designer and manufacturer of servo drives ultimately acquired by Lenze. In Scott's role as Global Product Planner for Kollmorgen, he has been very fortunate to find and even occasionally participate in some creative and fantastic experiments. Scott intends to use this blog to share interesting articles about new products or services that leverage a servo system, or use key components that one may find in a servo system. You can reach Scott here: Scott Evans
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