Weight Lifting Trajectory Optimization for Variable Stiffness Actuated Robot

Figure 3

Optimal deformation trajectories of variable stiffness actuated robot with GPM and iLQR. The blue dotted lines and the red dashed lines are the lower and upper bounds defined in (36) while they are not violated during the entire point-to-point motion. For comparison in the same time scale, the path parameter is introduced to scale different execution times into the nominal parameter space. And in the rest of paper, the comparisons among different actuators are also transformed to the parameter space.

(a) Actuator deformation with Gauss pseudospectral method (GPM)

(b) Actuator deformation with iterative linear quadratic regulator (iLQR)