It is shown that by integrating joint torque sensing and tactile sensor spatial and force information it is possible to increase the sensitivity in measuring the applied forces and contact locations. Using tactile sensors on a whole-arm manipulator (WAM) overcomes a number limitations in the joint torque method due to insufficient or low-accuracy measurements. In addition, a methodology is presented for determining design parameters for a tactile sensor given the requirements of a particular task. Specifically, the authors consider the design of a tactile sensor covering for the four-degree-of-freedom WAM arm installed at the MIT Artificial Intelligence Laboratory.>

The mechanical bandwidth of a manipulator ultimately limits its closed-loop bandwidth and so its response in both trajectory and force control. Here, mechanical design strategies are introduced to improve performance, including placing a distinct speed reducer at the joint rather than at the motor shaft, limiting the transmission ratio and properly selecting the contact compliance. The authors define simple models of the transmission for position-in-position-out and force-out and examine the corresponding transfer functions. The bandwidth of each of the simple models (which neglect damping) is approximately equal to the frequency of the first break point in the magnitude of the frequency response which, in turn, is equal to its lowest resonant frequency. The aim is for the open-loop bandwidth to be as high as possible to increase the quickness of the manipulator's response to commands.>

An approach to manipulation that uses all the available manipulation surfaces of the robot to act on and sense the environment is outlined. The kinematic, mechanism, actuation, and control implications of such a design are discussed and initial experimentation with a prototype mechanism are described. A three-degree-of-freedom underwater manipulator using a number of the resulting design concepts is described.>

We have studied the effect of Coulomb friction and stiction on force control with integral feedback. The force is applied through a compliant transmission by a velocity-controlled motor. Our results show that stiction can cause the applied force to enter a limit cycle. Coulomb friction can extend the system stability bounds but may lead to an input-dependent stability. Under certain conditions Coulomb friction causes an actuator limit cycle even though the applied force approaches the desired steady state force. Based on the analysis, we give design guidelines for increasing the performance.