Stable force controller design based on frequency response identification

Proposes a method of stable force controller design for robotic manipulators based on frequency response identification. The force controller described falls into the hybrid controller category. Force control loops are added to a popular position controller, enabling position control loops and force control loops to be designed independently. The proposed method does not require a detailed model of manipulator and environment dynamics. It is, therefore, robust enough for unmodeled dynamics, and easily analyzes stability in the high frequency region using the phase and gain margin method. The frequency response is identified by an accurate method called multi-decimation (MD), using motor input and contact-force output data. The MD method was previously developed by the author. The force control parameters (i.e. PID feedback parameters) are calculated by a stable design method called partial-model-matching (PMM), using the identified frequency response. The effectiveness of the proposed design method is demonstrated, through some experimental results, including a tracing task along a stiff environment, carried out using a planar two-link manipulator with harmonic drive gears