A system for assisting an operator in a manual assembly task includes a base assembly, end-effector, and controller. The base assembly has joint actuators providing three or more degrees of freedom (DOF). The end-effector is in series with the base assembly and has additional joints providing one or more additional DOFs. The base assembly and end-effector support a task load, including a weight and/or a reaction torque of an object. Sensors measure joint positions. The controller receives the measured positions, controls the joint actuators to support the task load, and extends a range of motion of the object. A method includes receiving the position signals as the operator manipulates the object, generating an output signal using the measured positions, and transmitting the output signal to the joint actuators to control the joint actuators, support the task load, and extending a range of motion of the object.