Use of Accelerometers in the Control of Practical Prosthetic Arms

Accelerometers can be used to augment the control of powered prosthetic arms. They can detect the orientation of the joint and limb, and the controller can correct for the amount of torque required to move the limb. They can also be used to create a platform, with a fixed orientation relative to gravity for the object held in the hand. This paper describes three applications for this technology, in a powered wrist and powered arm. By adding sensors to the arm making these data available to the controller, the input from the user can be made simpler. The operator will not need to correct for changes in orientation of their body as they move. Two examples of the correction for orientation against gravity are described and an example of the system designed for use by a patient. The controller for all examples is a distributed set of microcontrollers, one node for each joint, linked with the control area network bus. The clinical arm uses a version of the Southampton adaptive manipulation scheme to control the arm and hand. In this control form, the user gives simpler input commands and leaves the detailed control of the arm to the controller.