Feedback hybrid force and position control of an upper limb exoskeleton to support human movement

Abstract

In the paper, a feedback hybrid control including a force feedback control and a position control is proposed to control a four degree of freedom (4-dof) upper limb exoskeleton for supporting human movement at the shoulder, elbow and wrist joints. The novelty of the paper is that it has been able to control all the interaction forces at all links in the exoskeleton robot by using the proposed control. The desired interaction forces at the links and desired position are compared with the measured interaction forces and position, respectively. Then the torque at the shoulder, the torque elbow and the torque wrist joints are controlled to compensate the force error and the position error. The gains of the proposed controller are optimized by using the Balancing Composite Motion Optimization (BCMO). The simulation and control of the 4-dof upper limb exoskeleton using the proposed control is carried out in the paper to show that the interaction forces and the position of the exoskeleton track their desired values.

Feedback force and velocity control of an arm exoskeleton to assist user motion

“…The arm exoskeleton is controlled by the Eq. ( 3) [6], [12], [16]. The torques at revoluted joints are actuated by the servo motors and the user: The details of matrices in the Eq.…”

“…In phase 2, the desired feedback forces are generated to assist the user motion as follows [12], [13]:…”

“…5. In case of the original control [12], the optimal gains of the original control obtained by BCMO are: 𝐻 = 81, 𝐻 = 394. The optimal root mean square of error is:𝑅𝑀𝑆(𝑒 ) = 0.52 (N).…”

“…The force control is generalized to regulate the feedback force in [10], [11], and [18]. Recently the feedback hybrid force and position control method for assisting the user motion has been published in [12]. Although the force control was successful at controlling all the feedback forces on links, it contained many oscillations and errors.…”

“…The proposed control aims to improve the original control in terms of fast response and less oscillation. A scenario is proposed with two phases [11], [12].…”