A 3-DOF robotic model of a stick insect right middle leg is controlled using Sensory Coordinated Action Switching Modules (SCASM), under four different femur-tibia joint muscle model test conditions.  In sideways stepping the leg can easily get stuck pushing into the ground when the null muscle model is used, but a piecewise-constant muscle model allows reliable stepping in this case.  The adaptability of the SCASM step generation control to changes in substrate height is demonstrated using this case.  In forward stepping a linear muscle model at the FTi joint generates a smoother and (as shown in analyses in the paper) more regular stepping pattern than the piecewise-constant model.