Power-assisted wheelchair

A power-assisted wheelchair comprising:

• frame means;
• a drive wheel rotatably mounted on said frame means;
• a handrim connected with said drive wheel, with said handrim being angularly displaceable with respect to said drive wheel;
• power means including an electric motor mounted on said frame for causing rotation of said drive wheel when said motor is energized;
• sensing means for sensing angular displacement of said handrim relative to said drive wheel, said sensing means providing an output signal indicative of said displacement;
• and
• signal processing means for receiving said output signal from said sensing means and, responsive thereto, providing a control signal for causing energization of said electric motor, said signal processing means including first and second electronic feedback means providing velocity and acceleration feedback for conditioning said control signal to enhance said provided power-assist.

A power-assisted wheelchair comprising:

• a plurality of wheels at least one of which is a drive wheel;
• at least one handrim adjacent to and rotatable with respect to said drive wheel, said handrim being rotatable manually by a user to cause rotation of said drive wheel and thereby cause movement of said wheelchair;
• a capacitor torque sensor for sensing angular displacement between said handrim and said drive wheel including application of force insufficient to cause of itself a total desired movement of said wheelchair, said sensor including a first element having first electrically conductive means restricted to movement with said handrim and a second element having second electrically conductive means restricted to movement with said drive wheel, said first and second elements being closely adjacent to one another to form a capacitor the capacitance of which varies due to relative movement between said first and second elements;
• electronic circuit means connected with said first and second elements for developing a controlled signal responsive to the capacitance of said capacitor, said electronic circuit means providing an output indicative of said developed controlled signal;
• and
• a motor connected with said electronic circuit means to receive said output indicative of said developed controlled signal therefrom and, responsive thereto, causing said motor to propel said wheelchair to substantially achieve said total desired movement of said wheelchair.

In a wheelchair having a handrim and a drive wheel connected with the handrim through a plurality of spokes, a sensor for sensing displacement of the handrim of the wheelchair relative to the drive wheel, said sensor comprising:

• a plurality of strain gauges connected in an electrical bridge configuration having a plurality of legs connected with one another at different input and output connecting junctions, and with different ones of said strain gauges being connected in each said leg and to different ones of said spokes;
• electrical power means connected with said input connecting junctions of said strain gauges;
• and
• output means connected with said output connecting junctions of said strain gauges to provide an output indicative of the displacement between said handrim and said drive wheel as sensed by said strain gauges.

A centering device for automatically centering a handrim relative to a drive wheel associated with said handrim, said centering device comprising:

• spring arm means having a first portion adapted to be mounted on one of said drive wheel and handrim;
• roller contact means at a second position of said spring arm means spaced from said first portion;
• and
• spaced pin receiving means at the other one of said drive wheel and handrim not having said spring arm means mounted thereon, said spaced pin receiving means being adjacent to said roller contact means so that said roller contact means normally engages said spaced pin receiving means to establish a centered position, said roller contact means being urged toward said engagement with said spaced pin receiving means to automatically cause centering therebetween.

An electrical power-assist unit for a device having a movement producing unit and an actuator connected with said movement producing unit whereby manual manipulation of said actuator causes movement of the device, said electrical power-assist unit comprising:

• power means adapted to cause movement of the device when said power means is powered;
• sensing means for sensing manual manipulation of said actuator including application of force insufficient to cause of itself a total desired movement of the device, said sensing means including a capacitive element formed by first and second electrically conductive portions relatively movable with respect to one another with said first portion being caused to move relative to said second portion due to movement of said actuator, and with the capacitance established between said first and second portions varying due to said relative movement between said portions;
• and
• signal processing means electrically connected with said capacitive element of said sensing means and, responsive to the capacitance of said capacitive element, developing a controlled signal for causing powering of said power means to substantially achieve said total desired movement of the device.