A modular planar robotic manipulandum with end-point torque control

Abstract

Robotic manipulanda are extensively used in investigation of the motor control of human arm movements. They permit the application of translational forces to the arm based on its state and can be used to probe issues ranging from mechanisms of neural control to biomechanics. However, most current designs are optimized for studying either motor learning or stiffness. Even fewer include end-point torque control which is important for the simulation of objects and the study of tool use. Here we describe a modular, general purpose, two-dimensional planar manipulandum (vBOT) primarily optimized for dynamic learning paradigms. It employs a carbon fibre arm arranged as a parallelogram which is driven by motors via timing pulleys. The design minimizes the intrinsic dynamics of the manipulandum without active compensation. A novel variant of the design (WristBOT) can apply torques at the handle using an add-on cable drive mechanism. In a second variant (StiffBOT) a more rigid arm can be substituted and zero backlash belts can be used, making the StiffBOT more suitable for the study of stiffness. The three variants can be used with custom built display rigs, mounting, and air tables. We investigated the performance of the vBOT and its variants in terms of effective end-point mass, viscosity and stiffness. Finally we present an object manipulation task using the WristBOT. This demonstrates that subjects can perceive the orientation of the principal axis of an object based on haptic feedback arising from its rotational dynamics.

A key region in the human parietal cortex for processing proprioceptive hand feedback during reaching movements

“…However, utilizing robotic manipulanda for recording and manipulating movements is quite common in reaching research (cf. references in Howard et al (2009)), and especially experimental manipulations such as the force perturbation are not possible with free reaching. Since we only compared movements executed with a manipulandum, we do not believe that the spatial and temporal TMS effects observed stemmed from our particular experimental setup.…”

Integrating actions into object location memory: A benefit for active versus passive reaching movements

“…A Queen's University ethics committee approved the protocol. While seated, the participant grasped a vertical handle attached to a lightweight planar robotic manipulandum (vBOT, Cambridge University, [13]) that moved in a horizontal plane (Fig. 1A).…”

Adaptation to visuomotor rotation in isometric reaching is similar to movement adaptation

“…2C). The air bearing design, modeled after [15], features a triangular base with 3 air jets localized at the corners, and an arm support with Velcro straps. The arm moves with minimal friction over an adjustable glass-top table, and the wrist is constrained with a brace.…”