To let above-knee amputees walk with a natural gait, ISRO has developed an intelligent artificial limb that offers extended capabilities for the amputee than those provided by the passive limbs that do not use microprocessors.
Weighing about 1.6 kg, these microprocessor-controlled knees (MPKs) detect the state of gait based on the sensor data. It consists of a microprocessor, hydraulic damper, load & knee angle sensors, composite knee case, Li-ion battery, electrical harness, and interface elements. The stiffness of the device is controlled by a hydraulic damper driven by a DC motor, and the control software calculates the real-time damping required to achieve the desired gait.
One can establish walking characteristics customized to amputees to increase comfort using computer-based software. In real-time, as you’re walking, the interface plots the parameters.
To develop this MPK, the team first arrived at a configuration theoretically. Then validated through kinematics analysis for estimating the subsystem requirements. Later on, multiple models of the system were developed.
Using an engineering model, the design’s viability was confirmed. The system comprised a six-axis load cell, a solenoid valve-based damper, and an aluminum knee case. The following engineering model included a DC motor-based damper with a spool position sensor, pylon integrated load cell, miniaturized control electronics, and a Graphical user interface for parameter adjustment. In contrast, the previous model utilized a stepper motor-based damper and composite knee casing.
The hydraulic damper, control electronics, and load cell, which are the limb subsystems, were tested and characterized in stand-alone mode using customized setups—using an exo-socket that was specially created for the purpose allowed for an imaginative way to be developed for conducting the walking trials with non-amputees. The control software may be updated, and the parameters could be adjusted through multiple walking experiments with non-amputees.
When the Joint Project Monitoring Committee (JPMC) approved, the gadget was tested with an amputee chosen by NILD to participate in walking trials. NILD and VSSC jointly conducted the testing at the NILD lab.
The socket and fitment of MPK to amputee were realized NILD. VSSC tuned amputee-specific parameters. Initial walking trials were conducted with the support of parallel bars. Subsequently, the amputee could walk about 100 m in the corridor with minimum support. All the subsystems of the knee performed satisfactorily.
The MPK is projected to be commercialized shortly and will be around ten times cheaper than current options, reported ISRO.
These smart MPKs are being developed by Vikram Sarabhai Space Centre (VSSC), ISRO under an MoU with National Institute for Locomotor disabilities (NILD), Pt. Deendayal Upadhyaya National Institute for Persons with Physical Disabilities (Divyangjan) (PDUNIPPD (D)), and Artificial Limb Manufacturing Corporation of India (ALIMCO).