Improving Robotic Force Control Performance in Devices With Force Measurement and Modeling Error

This article investigates methods for improving the robot force control performance in situations, where the force measurement error is unavoidable, such as exoskeletons, low-cost sensors, and flexible robotics. When using force control strategies such as impedance control (IC) and admittance control (AC) in these situations, we propose that it is important to consider their inherent robustness to either force measurement error or modeling error. The improper choice of controller can lead to increased error, undesired interaction behavior, and even instability. Furthermore, we propose that interpolation with unified interaction control (UIC) can tradeoff these two robustness properties and, in some cases, can improve performance. A case study using a low-cost force sensitive resistor with less accuracy than traditional force/torque sensors is conducted. The results illustrate that, even when force measurements do not reach the accuracy of traditional sensors, an accurate rendering ofthedesired impedance can be achieved by careful selection of the controller.