Contact Stiffness Identification with Delay and Structural Compensation for Hardware-in-the-Loop Contact Simulator

The hardware-in-the-loop (HIL) simulation is necessary to test the contact dynamics of spacecraft in space. The stiffness parameter is important for the state recording and compliant control. A contact stiffness estimation method is proposed, where the force measurement delay and structural dynamics of the upper platform are compensated to guarantee the estimation accuracy. The force measurement delay and structural deformation of the upper platform lead to the delayed force signal and the position error respectively, and then the contact stiffness identification error. A phase lead based delay compensation is used to reconstruct the true contact force from the measured force. The structural deformation of the upper platform is compensated by a structural dynamics model to obtain the true contact position. Based on the compensated force and position signals, the stiffness identification is performed using the real time recursive least squares (RLS) method. The effectiveness of the proposed method is verified by simulations and experiments. In the experiments, the stiffness identification error is about ± 5 %, which is satisfactory for monitoring and control applications.