Controlling a 3 DOF spatial point motion with 4 motors in a 4 DOF system affords an extra DOF from which transmission characteristics may be geometrically defined. For example, the endpoint may be held fixed, and backdrivability characteristics may be modulated. This can be a nice feature given EM motors dual role as both actuators and sensors in proprioceptive designs, which pose competing geometric requirements (force amplification vs backdrivability).