Doctoral Thesis

Robotics have shown tremendous developments, such as industrial robots that assist us in production lines in manufacturing such as KUKA, FANUC and mobile robots in our everyday lives/work that perform various tasks such as material handling or inspection in hazardous environments, space exploration as well as entertainment or services that involve interaction with humans or objects. Many of these robot designs are driven by servo motors that actuate the joints, i.e. classical two link planar robot manipulator design. Some designs include pulleys, ball screw, gears and other mechanisms. Although these options produces acceptable results for position control, problems such as Coulomb friction, backlash, backdrivability are not negligible. Thus researchers started venturing into direct-drive actuators that eliminate such problems and have come up with several solutions such as harmonic drive and twin drive differential gear system. However, these solutions results in relatively low torque/thrust volume densities, i.e large and heavy motors to support large torque/forces. Others propose tubular linear permanent magnet motors as an option for linear/prismatic actuation to replace servo motor coupled with ball screw or other mechanisms. A biarticular manipulator is a musculoskeletal manipulator that consists of links and muscles. For a two-link arm, muscles consist of two pairs of monoarticular muscles (muscles that actuate single joint) and a pair of biarticular muscles (muscles that actuate two joints simultaneously). A pair of muscles means flexor and extensor muscles that push or pull arm links. A new manipulator design using direct-drive spiral motors is presented. One spiral motor can represent a pair of flexor/extensor muscles thus reducing the number of muscles in the biarticular manipulator from six to only three. This is because the spiral motor is a three-phase Permanent Magnet direct-drive linear actuator that provides high thrust force in forward/reverse direction without any transmission mechanism (gears/belt/pulley). Control of the spiral motor is experimentally validated by simultaneously maintaining rotational angle and gap between stator and rotor (magnetic levitation). Due to the complexity of the closed-link musculoskeletal manipulator and two degree-of-freedom spiral motors, kinematics and dynamics is derived to address spiral motor current inputs and force/torque outputs. Although actuatorlevel control can be easily achieved, workspace control requires kinematic redundancy of the manipulator to be resolved, which is investigated in position and force control in workspace domain.