Robot Force Control
In many applications, a robot must explicitly control the force it applies to the object it is manipulating. The actuators must be controlled to achieve the desired forces.

Joint Torque Control

A force (a vector of three forces and three torques) are controlled in Cartesian space by controlling torques in joint space. From robot statics, the transformation between joint space torques and Cartesian
space force is the transpose of the manipulator Jacobian.

Torque in joint space is controlled by controlling the torque applied by each actuator. Torque can be measured using a sensor (accurate) or calculated from armature current (simple).

Force control using feedback of joint torques is limited by the accuracy of the static model of the manipulator. To obtain accurate control of the force vector at the end effector, place a wrist force sensor between the tool plate and the end effector to measure end effector force. The force transform from the sensor to the end effector is usually simple.