Soft Power Wheelchair

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Torque control
Power assist wheelchairs work best when there is a torque feedback, measuring the user input torque and using it to determine the torque the motor needs to supply to the wheels. But this method has not been able to reach the masses especially in developing countries because torque sensors are comparatively very expensive and are not affordable for customers from below the upper class. Soft-sense uses a new alternative to torque sensors which can be made much cheaper and also allows for other functions. Series elastic actuators are an area of research in robotics that has enabled among other functions, torque control by using a series element with the motor and measuring displacements. Using this in wheelchairs essentially means that the same effect as that of the torque sensor can be obtained by using a spring and two encoders (or any other position or feedback sensor) costing only a mere fraction of the original cost.

Force amplification
Furthermore this design uses ratchets to enable the device to also work as a parallel elastic actuator, (another related research area). When the user encounters a bump or a significantly large obstacle, the user input and the motor input together also might not be sufficient for climbing over. In such a situation the design allows the user to store the energy from a single stroke in the spring and enables him to freely move back and come back for the next stroke, this time availing the force from the user and the energy from the springs and the motor torque enabling the device to produce very high torques significantly larger than even the motor and human effort together to climb over larger obstacles. This can especially facilitate climbing over stairs, which can significantly increase the mobility of the user.

There can also be other modification like motitoring where the user holds the lever to determine the amount for torque control level is to be used. This can also enable further developments in wheelchairs in providing large amount of energy in a short span of time as in climbing over obstacles


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  • Name:
    Ashish Vasant
  • Type of entry:
  • Patent status: