Experimental Identification of Friction and Dynamic Coupling in a Dual Actuator Testbed

In this paper our objectives were to present the methodology and results for the experimental identification of two performance-limiting phenomena in a differential-based dual-input actuator testbed: (i) velocityand position-dependent friction and (ii) dynamic coupling between the dual inputs. The contributions of this paper are as follows: (i) experimental methodology to characterize the dynamic coupling in the dualinput actuator and (ii) methodology and data analysis for friction identification in a dual input actuator. We have leveraged and replicated experimental procedures on friction identification reported in the literature. The Stribeck-effect and viscous damping effects were determined with an average repeatability of 3σ = 5.6% using constant velocity experiments. Position dependent friction was determined using spatial FFT analysis of torque data with a variance of 3σ = 0.56%. Dynamic coupling was determined using an experimental set up where the torque disturbance on one branch of the dual-actuator is measured during the periodic motion of the other. Crosscorrelation analysis determined that, in our testbed, the coupling was well correlated (r = 0.9726 and 3σ = 3.6%) with velocity of motion. The implication of our results is that the methodology and data analysis techniques outlined in this paper provide a first step towards the experimental certification of dual-input actuators.