# US 11,432,977 B2 · Power assist wheelchair, power assist unit for wheelchair, control device for power assist wheelchair, control method for power assist wheelchair, and program

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- Number: US 11,432,977 B2
- Document ID: US11432977B2
- Status: Granted
- Kind: B2
- Application number: 16/624,933
- Filed: 2017-06-26
- Published: 2021-11-04
- Granted: 2022-09-06
- Earliest claimed: 2017-06-26
- Assignees: Yamaha Hatsudoki Kabushiki Kaisha
- Applicants: Hisashi Takahashi; Yamaha Hatsudoki Kabushiki Kaisha
- Inventors: Hisashi Takahashi; Tatsuki Uemura; Masamitsu Mizuno
- Web page: https://patentgrep.com/patent/US11432977B2

## CPC

- A61G 5/048: {Power-assistance activated by pushing on hand rim or on handlebar}
- A61G 5/02: propelled by the patient or disabled person
- A61G 5/04: motor-driven (A61G5/06 takes precedence; motor-operated rests A61G5/12; for vehicles with handlebars, equipped with three or more wheels B62K5/003, B62K5/023)
- B60L 15/20: for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
- B62M 6/50: characterised by detectors or sensors, or arrangement thereof
- B60L 2200/24: Personal mobility vehicles
- B60L 2200/34: Wheel chairs
- B60L 2240/421: Speed
- B60L 2240/423: Torque
- B60L 2240/429: Current
- A61G: TRANSPORT, PERSONAL CONVEYANCES OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS (appliances for aiding patients or disabled persons to walk A61H3/00); OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES (embalming corpses A01N1/00)
- B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B62M: RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR {SINGLE-TRACK} CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES (arrangements or mounting of transmissions in vehicles in general B60K; transmission elements per se F16)

## Abstract

A power assist wheelchair includes a wheel, an electric motor that drives the wheel, an encoder that detects rotation of the electric motor, and a control device that controls the electric motor. The control device includes a total torque value calculator that calculates a total torque value based upon only a detection signal of the encoder, an assist torque value calculator that calculates an assist torque value based upon an output current of the electric motor, a manual torque value calculator that calculates a manual torque value based upon a difference obtained by subtracting the assist torque value from the total torque value, and a target current determiner that determines a target current of the electric motor based upon the manual torque value.

## Claims

### Claim 1

A power assist wheelchair comprising:
a wheel;
an electric motor that drives the wheel;
an encoder that detects rotation of the electric motor; and
one or more processors to control the electric motor and configured or programmed to function as:
a total torque value calculator configured or programmed to calculate a total torque value based upon a detection signal of the encoder;
a twist torque value calculator configured or programmed to calculate a twist torque value representing torque causing twist of the wheel with respect to an axle;
a manual torque value calculator configured or programmed to calculate a manual torque value based upon a difference obtained by subtracting the twist torque value from the total torque value; and
a target current determiner configured or programmed to determine a target current of the electric motor based upon the manual torque value; wherein
the twist torque value calculator is configured or programmed to calculate the twist torque value based upon a difference obtained by subtracting a torque value calculated based upon the detection signal of the encoder from an assist torque value calculated based upon a current outputted to the electric motor.

### Claim 2 (depends on 1)

The power assist wheelchair according to claim 1, wherein the total torque value calculator calculates the total torque value based upon a difference obtained by subtracting a twist angular velocity value representing an angular velocity of the twist from an angular velocity value calculated based upon the detection signal of the encoder.

### Claim 3 (depends on 2)

The power assist wheelchair according to claim 2, wherein the twist angular velocity value is calculated based upon the twist torque value.

### Claim 4

A control method for a power assist wheelchair including a wheel, an electric motor that drives the wheel, and an encoder that detects rotation of the electric motor, the method comprising:
calculating a total torque value based upon only a detection signal of the encoder;
calculating an assist torque value based upon a current outputted to the electric motor;
calculating a twist torque value based upon a difference obtained by subtracting a torque value calculated based upon the detection signal of the encoder from the assist torque value calculated based upon the current outputted to the electric motor;
calculating a manual torque value based upon a difference obtained by subtracting a torque value obtained from the twist torque value from a total wheel torque value obtained from the total torque value;
determining a target current of the electric motor based upon the manual torque value; and
controlling the electric motor based upon the target current of the electric motor.