  Collaborative robots should ideally use low torque actuators for passive
safety reasons. However, some applications require these collaborative robots
to reach deep into confined spaces while assisting a human operator in
physically demanding tasks. In this paper, we consider the use of in-situ
collaborative robots (ISCRs) that balance the conflicting demands of passive
safety dictating low torque actuation and the need to reach into deep confined
spaces. We consider the judicious use of bracing as a possible solution to
these conflicting demands and present a modeling framework that takes into
account the constrained kinematics and the effect of bracing on the
end-effector compliance. We then define a redundancy resolution framework that
minimizes the directional compliance of the end-effector while maximizing
end-effector dexterity. Kinematic simulation results show that the redundancy
resolution strategy successfully decreases compliance and improves kinematic
conditioning while satisfying the constraints imposed by the bracing task.
Applications of this modeling framework can support future research on the
choice of bracing locations and support the formation of an admittance control
framework for collaborative control of ISCRs under bracing constraints. Such
robots can benefit workers in the future by reducing the physiological burdens
that contribute to musculoskeletal injury.
