Fig. 13From: Evaluation of three force-position hybrid control methods for a robot-based biological joint-testing systemHistories of the force and moment components during the VV test at 30° knee flexion. Changes of all the force and moment components during the constrained VV test (a CT), and unconstrained AP tests using (b) FPH, (c) FPA and (d) FPHFM. While the constraining forces (AP, PD and LM) and moments (IE) were quite large during CT with RMS values of up to 9.3 N and 0.22 Nm, respectively, their values were greatly reduced during unconstrained tests (b–d). The FPHFM was able to keep the constraining forces and moments close to the measurement accuracy, with RMS values of less than 4.9 N and 0.07 Nm, respectively, and the RMS values of FE angles less than 0.28°. The FPH had RMS values of up to 7.9 N and 0.13 Nm for the constraining force and moment components, respectively. The values for FPA were in between the FPHFM and FPHBack to article page