Figure 8 plots the joint torques on the middle leg during the stance stage for both the simulated and real cases. The torque from the simulation cases are recorded as the torques applied on the joint constraints during the simulation step. The torque from the real cases are computed with the method of Virtual Model Control11. This method is based on Jacobian matrix, converting the ground force on the end-effector into the joint torques given the configuration of body hierarchy. The peak of the simulation torques arises in the first half of the stance stage for the body-coxa and femur-tibia joints, and in the middle of the stance stage for the coxa-femur leg. However, the muscle activation in the simulation case reaches its peak around the end of the stance stage, instead of the first half. This is possibly due to the fact that the joint rotation reaches its limit at the end of the stance stage, resulting in a small value of FL and FV (Equation 9) and thus a moderate value of joint torque. The torque profiles of real cases generally follow the shape of a parabolic curve and have the peak value around the middle of the stance stage. This is consistent with the ground force on the middle leg (Fig. 9(b)), which presents a similar parabolic curve shape.Figure 8Joint torques on the middle leg during the stance stage in the mode of walking straight forward.Figure 9Ground forces in the Z direction during the stance stage in the mode of walking straight forward.