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CANADARM 2

CANADARM 2

The David Florida Laboratory Participates in Canada's Premier Robotics Development Project

The original Canadarm went into space for the first time more than 20 years ago. It has since flown on nearly 70 space shuttle missions. Designed and built by Spar Space Robotics, now MacDonald Dettwiler Space and Advanced Robotics Ltd (MD Robotics), the first Canadarm cost about $100 million. It was Canada's contribution to the U.S. Space Shuttle Program. NASA has since ordered four more units, at a cost of about $600 million.

Canadarm 2, is now a significant component aboard the International Space Station (ISS). The contribution of the Mobile Servicing System (MSS) which includes the Canadarm 2, represents Canada's contribution to the International Space Station.

The Canadian Mobile Servicing System or MSS, is an essential component of the International Space Station. The system has three parts:

  • Canadarm2, the Space Station Remote Manipulator System (SSRMS) - delivered to the ISS in 2001;
  • the Mobile Base System (MBS) - a work platform which will move on rails along the length of the space station - delivered to the ISS in 2002;
  • the Special Purpose Dexterous Manipulator (SPDM) - a "robotic astronaut" which has two arms of its own - scheduled for delivery in 2004.
The MSS gives astronauts the ability to move equipment and supplies around the space station. It provides
the only way to manipulate objects outside of the space station without having a human actually leave the relative safety of the space station.

THE SPECIAL PURPOSE DEXTEROUS MANIPULATOR OR SPDM

Gary Searle is an MD Robotics Program Manager who has just completed two years working at the David Florida Laboratory, testing the components which will make up the Special Purpose Dexterous Manipulator or SPDM. We asked Gary why he thought the Canadarm 2 system was important for Canadians.

He responded, "Projects like the Canadarm 2 bring Canadians into the forefront of technology, we become pioneers rather than followers. The capability that MD Robotics has developed by building the Canadarm systems for the Canadian Space Agency has made us world leaders in our particular field of robotics. We have no real competition. Organizations from all over the world, including the U.S. and Japan are coming to us with their requirements."

The project that Gary Searle worked on until recently was the Special Purpose Dexterous Manipulator or SPDM. This is a system that will allow the Canadarm 2 to do more intricate work than it can currently do using its end effector, or mechanical hand. The current end effector is suitable grasping a large object such as a satellite or a component to be added to the ISS.

The SPDM which will be added in 2004, is designed, as you would expect from its name, to carry out tasks that require more dexterity. Using two arms, each having its own much smaller more specialized end-effector, called an Orbital Tool Change-out Mechanism or OTCM. The OTCM is specifically designed to grasp the small attachment devices used to secure equipment and electronic boxes to the outside of the space station. These attachment devices are in turn referred to as micro fixtures.

Taken as a whole, the two armed SPDM with its specialized end effectors, can be thought of as the space station's robotic external maintenance technician. Fully controllable from within the station, astronauts will be able to service most aspects of the outside of the station without being exposed to the hazards of a space walk.

THE ROLE OF THE DAVID FLORIDA LABORATORY IN THE SPDM DEVELOPMENT

"Space is a totally different environment from earth", explains Gary. "We encounter atomic Oxygen, no breathable air, extreme temperatures that fluctuate, vacuum conditions and high vibration conditions on launch. Every system is effected differently by these conditions and every system must be designed and tested in ways that take these conditions into account."

The David Florida Laboratory (DFL) is the expert at simulating space conditions. Every moving component of the SPDM was put through rigorous testing at the DFL. Some of the types of testing available at the lab include:

Vacuum Testing
In space most lubricants outgas. This means that over time lubricants completely disappear. As a solution, specialized lubricants that avoid this problem have been developed. That is one of the reasons that mechanisms intended for use in space must be tested in a vacuum test chamber like the ones available at the DFL. Another reason is that many mechanisms such as braking systems are designed to operate only under vacuum.

Vibration Testing
When the DFL first receives a component, one of the first set of tests that could be performed are continuity and isolation tests. This means that the device would be tested at normal room temperature and pressure to make sure that it operates as expected.

Once continuity testing is passed, a component could be taken into the vibration facility where it would undergo vibration testing along 3 different axes. The vibration level would be typical of that experienced during launch. This is the so called launch load. Vibration tests are also done in order to check workmanship.

Extreme Temperature Testing
Space is a place of extreme temperatures. Any equipment designed to operate successfully in that environment must endure sudden shifts between extreme heat and extreme cold. The DFL test chambers provide a facility where space bound components can be tested operationally under vacuum and through extreme temperature variations ranging typically between plus 70 and minus 36 degrees Celsius.

Gary
  
The Canadian Mobile Servicing System or MSS has three main parts:
Canadarm2, the Space Station Remote Manipulator System (SSRMS) - delivered to the ISS in 2001; the Mobile Base System (MBS) - a work platform which will move on rails along the length of the space station - delivered to the ISS in 2002; the Special Purpose Dexterous Manipulator (SPDM) - a

The Canadian Mobile Servicing System or MSS has three main parts:
  • Canadarm2, the Space Station Remote Manipulator System (SSRMS) - delivered to the ISS in 2001;
  • the Mobile Base System (MBS) - a work platform which will move on rails along the length of the space station - delivered to the ISS in 2002;
  • the Special Purpose Dexterous Manipulator (SPDM) - a "robotic astronaut" which has two arms of its own - scheduled for delivery in 2004.
Searle talked about his experience at the DFL where the SPDM components were tested. "Any components that had brakes were tested under thermal vacuum. Space brakes are designed to work in vacuum to operate. We put our systems into the DFL thermal vacuum chamber in order to test them. We would run the motors and then hit the brakes. The cycle would be repeated several times under hot conditions and then during cold to run in the brakes. It takes about 2 weeks to perform a complete set of tests, a week for thermal vacuum testing, a day and half to do the vibration testing and then all the ambient testing that has to be done in between."

THE IMPORTANCE OF CONTINUITY

We asked Gary about what it took to be successful in the space robotics industry. Gary's immediate response was, "Continuity". Many of the engineers at MD Robotics and at the David Florida Lab that helped build the original Canadarm have now retired. However, they personally trained people like Gary who are in turn training a new generation of engineers who will pick up the skills needed, and the lessons learned, to address the even more demanding requirements to come in the future. "Passing on the torch is critical because this is something you can't learn in a book.", says Gary.

Gary is very satisfied with his career at MD Robotics, he explained, "Having the opportunity to work on this type of hardware is rare. We are able to attract the best and the brightest out of university and train them to carry on. Furthermore our products are unique in the world. Nobody else does what we do. We've gained the respect by NASA and other countries for those very reasons."

NEW HORIZONS

Gary Searle is now the program manager of what is called the " neuroArm". Using much of the same technology that went into the Canadarm, MD Robotics is building a robot arm which will be used to carry out brain surgery while the patient is placed in an MRI. Working on a smaller scale than the SPDM the neuroArm requires similar levels of precision, safety and user control as those required in space.

Features which will make the neuroArm unique include:

Haptic Control
The neuroArm will have a variety of surgical instruments attached, such as forceps and specialized instruments used to hold, cut and cauterize tissue. The instruments MD Robotics is developing for the arm will be almost identical in appearance to normal instruments, except for how they are held. When the operator, a surgeon, uses these instruments to touch a piece of tissue they will "feel" the force that the tool is applying to the tissue through the hand controllers.

This kind of sensory feed back to the operator is called "Haptic control". The surgeon will sit at a work station located outside the operating room where the patient is located. It will be the robot that does the surgery. "Haptic control" is a capability unique to neuroArm in the field of surgical robots, as none of the currently available surgical systems offer this feature.


Optical Force Sensor
MD Robotics has developed an optical force sensor. In order to achieve "Haptic control", force is usually measured using a electrical/mechanical sensor, and then electrical signals are transmitted to the feedback devices within the hand controller. However common electrical sensors cannot operate correctly within the MRI environment. To solve this problem MD Robotics has invented and patented a purely optical force sensor that communicates the force load on it by way of reflected light from a fiber optic probe. No electrical signals or attachments are required.

Canadarm Software
The technologies needed for the development of the neuroArm are very similar to those used in the Canadarm 2, except that the scales are much smaller. The neuroArm needs to get around in tighter areas, but the fineness of motion is the same. If you imagine your own shoulder moving a quarter of an inch, your arm will have moved almost a foot. The accuracy in the Canadarm has to be very precise at the shoulder in order to get the accuracy needed at the end of the arm.

The neuroArm requires 1mm resolution of movement in order to be able to suture small arteries. The mechanical parts have to be very accurate as well. MD Robotics will need to machine some components to within two one one thousandths of an inch, much the same tolerances as those required in the Canadarm 2.

What is really critical in both of these applications is the software that enables the arms to move. A good portion of the software being used in the neuroArm came from the Canadarm projects. In space the safety systems have to be as perfect as they do in brain surgery. You can't risk having the arm start jerking in space when the lives of personnel or the safety of valuable equipment is at stake.

Applications of Canadarm technology do not stop at neuro-surgery. MD Robotics manufactures mining robots, vision systems that detect ice and chemicals from a distance. MD Robotics has even sold dinosaur robots to Universal Studios. These animated triceratops won a gold award at the recent Design Engineering Awards. According to the award announcement,

"While not a manufacturing system, the entry is used as commercial equipment by Universal Studios Islands of Adventure. The complex programming and smooth motion control systems make for a stunningly real illusion to customers who are never more than six feet away from the exhibit-sometimes even touching it. The dinosaur has a range of realistic behaviour-dilating pupils, coordinated muscles and tongue movement among them-a striking simulation of a live animal."



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