Projects
Wearable Robotics
Cable-Driven Robotics (CDR)
Development of a portable sensor system for movement characterization and performance measurement:
Every individual has a different walking style resulting in person-specific gait characteristics. In order to improve the quality of training received by the neurologically affected patients, we believe there is a need to develop sensor systems which are capable of providing subject-specific gait assessment and diagnosis. At the same time, it should be lightweight, durable, and wearable so as to generate and assess gait data while performing mundane day-to-day activities. At HCR Lab, we have developed a wearable sensor system called “Intention Detection and Gait Recognition” (IDGR) System. It consists of three subunits: one pelvis and two-foot units. Presently, this system is able to detect gait events (heel-strike and toe-off), provide temporal gait parameters (stride time, step time, stance and swing time, gait asymmetry, cadence, fundamental frequency of walking). The system uses adaptive frequency oscillators to provide instantaneous knowledge of the gait phase of the subject.
Performance analysis of cable-driven manipulators:
Cable-driven manipulators, due to the unilateral force application property of cables, are redundantly actuated systems compared to rigid link counterparts. Thus, the understanding generated from conventional rigid-link robots cannot be extended to cable-driven systems. Thus, in this project, we are focusing on understanding the performance of cable-driven manipulators, i.e., workspace, manipulability, and manipulator interaction with surroundings. Further, the dependency on manipulators’ performance on the cable-routing architecture is studied.
Cable Driven Leg Exo-skeleton:
As part of this project, a cable-driven leg-exoskeleton, assisting human lower limb sagittal plane motion is currently under development at the lab. Exoskeleton aims at applying an external wrench at hip and knee joints, via actuated cables, through thigh and shank cuffs worn by a human. Currently, studies are happening in identifying suitable cable-routing architecture for effective human-robot interaction. Further, during walking with the exoskeleton, the human motion will be monitored in real-time using a motion capture system. A real-time optimization scheme and controller which uses the motion data to compute the desired cable tension values that are to be applied during human motion is under development.
Musculoskeletal modelling, musculature and skeleton, of human limbs as CDR:
In this work, the lower limb musculoskeletal system is modelled as a cable-driven serial chain system. This model is used to study the stiffness variations during a movement task, which further can be useful in designing better human-robot interaction paradigm. Multi-joint and taskspace stiffness matrices are formulated for the lower limb musculoskeletal system by considering dominant muscles during the swing and single support stance phase of walking as cables. Various joint stiffness parameters are formulated to study the role of dominant muscles in altering the multi-joint and taskspace stiffness values.
Human-Quadcopter Interaction
Motor Adaptation
More details to be added soon.
Other Projects
Active Tethered Pelvic Assist Device (A-TPAD):
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, 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.
Locomotor Adaptation Study using the A-TPAD:
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 holds great potential in the gait rehabilitation process.
Perturbation Study using the A-TPAD:
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.
Effect of Spring on Wrench Feasible Workspace:
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.
Second Spine:
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.
Gravity-Balanced Passive Mechanism:
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.
PD Shoes:
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 vibrotactile feedback can help improve the gait performance of PD patients.