Joint Stiffness Testing with the Adept Robot

This page seeks to layout testing with the Adept robot. Experimental tests done by others have suggested that the only mass that matters during a robot-human collision is that of the most distal link, irrespective of how it is connected to the rest of the robot. This series of tests seek to investigate this phenomenon further by performing impacts with a robotic manipulator that has a passive joint of variable stiffness. By varying the stiffness of the joint, we hope to show the effects of joint stiffness and inertia coupling. This may allow us to attribute the experimental results seen by others tothe Zero Order Hold inherent to stiffness supplied by motors or the result of backlash (slop) in the mechanisms. The following is a list of subsections that need to be done to complete these tests.

• Sensor redesign
  • Currently the sensor strips are designed to be sampled one at a time. In addition, there is a certain time lag associated with turning on a sensor pad. Ideally, the sensor strips are to be modified to be on all the time and simultaneously monitored.
  • SensorUpdate
• Sensor interrogation
  • Currently, the sensors are interrogated using a PIC. The maximum data rate associated with each sensor achieved was 240 Hz (4 sensors), insufficient to capture the high speed impact data desired.
  • XPC is considered to be the prime cadidate for achieving desired data rates. A program in simulink needs to be written to that the DAQ card receives waveform data from the sensor and translates it into a frequency value. This can either be done in real time or afterwards via postprocessing.
  • InterrogationUpdate
• Target Design
  • Sliding contact is desired for testing the sensitivity of the sensors, so the target must be sufficiently smooth with a low coefficient of friction. A cylindrical form is desired as it most closely mimics a headform.
  • TargetDesignUpdate
• Adept Trajectory planning
  • A very short term project. The Adept is a quintessential manufacturing robot, designed to work without humans nearby. They are typically found in fully automated work areas. A collision with such a robot could potentially be dangerous. In order to perform accurate tests, the robot must be assigned specific trajectories with known configurations during collision.
  • AdeptUpdate?
• Arm Simulant Design
  • The robotic arm simulant is designed to allow variation in joint stiffness. There will be a distal section in order for it to strike the target.
  • ArmSimulantUpdate