Research

In this work, a cable-driven robot, the Active Tethered Pelvic Assist Device (A-TPAD), has been developed at the ROAR Lab, Columbia University to scientifically study adaptation in human walking. The A-TPAD applies external wrench (force and moment) on a hip belt, worn by a human, via actuated cables. During walking with the A-TPAD, the human motion is monitored in real-time using a motion capture system. An online optimization scheme uses the motion data to compute the desired cable tension values. A low-level force mode controller applies the desired external wrench with positive cable tension during the human motion.

People with hemiparesis exhibit gait asymmetry due to reduced weight bearing on their affected side. In this work, a novel experimental paradigm using the A-TPAD was proposed for the gait rehabilitation of hemiparetic patients. A force vector intended to provide external weight bearing during walking to alter the limb support periods was applied on the pelvis. An experiment with ten healthy subjects showed asymmetric locomotor adaptation to the applied force, implying possible recalibration of the motor commands. Such motor adaptation to the external interventions hold great potential in the gait rehabilitation process.

People develop balance deficits during walking with age and due to neural impairments resulting in risk of falls and serious injuries. Training programs involving repeated unexpected perturbations can induce adaptation mechanisms to modify the reactive and proactive strategies to control dynamical gait stability. In this work, the A-TPAD was used to apply unexpected multi-directional waist-pull perturbations. Healthy subjects showed adaptive changes in the reactive and proactive control of stability.

In cable-driven parallel robots (CDPRs), it is usually challenging for the wrench-feasible workspace (WFW) to meet the design requirements. Therefore, redundant cables or load on the end-effector is used to attain the required workspace. In this work, springs were added between the end effector and base with the goal to modulate the workspace. The effects of spring parameters on the CDPR's wrenches were investigated and an optimization was proposed to determine the feasible spring parameters. An experiment using the A-TPAD showed that springs can increase and/or reshape the WFW of CDPRs to meet the specified design requirements.

In this work, a vest, the Second Spine, has been developed to prevent musculoskeletal injuries caused by heavy backpack loads, while also maintaining the range of motion of the wearer. The vest is formed by multiple segments between the shoulder and a pelvic belt. The stiffness of the Second Spine structure is adjustable, such that in normal “off” configuration, the segments are disconnected from each other and the vest is flexible providing full range of motion to the upper body. With the pull of a string in the “on” configuration, the vest becomes semi-rigid creating a secondary pathway to transfer loads between the shoulder and a pelvic belt.

In this work, a Constant Pushing Force Device (CPFD) has been developed to apply an external constant force on the subject’s pelvis. Two extension springs within the serial-chain architecture of the CPFD balance the device’s gravity and exert a constant force regardless of the pelvis motion. Adapting such passive mechanisms in the design process of robotic exoskeletons can help reduce the active joint torque requirements.

Shoes that can provide step-synchronized vibrations using force sensitive resistors and vibrators were developed. Pilot experiments with Parkinson’s disease (PD) patients, at All India Institute of Medical Science New Delhi, showed that the external vibro-tactile feedback can help improve the gait performance of PD patients.

A mobile robot based wheelchair for adults using a force feedback joystick was developed to provide an assist-as-needed feedback. Experiments to study driving skills improvements were conducted using the line following and potential-field based point following algorithms.