A power-assisted wheelchair (1) having an electric motor (32), a potentiometer (27) as means for detecting human power applied to wheels (2), and a controller (31) as means for controlling the electric motor (32) according to the detected human power so as to set the time-attenuation rate of the assist power to be greater as the human power is smaller, and to be smaller as the human power is greater. Therefore, the coasting amount of the wheelchair (1) for small indoor movements for example is restricted to a small value. As a result, small indoor movements with a small turning radius are made possible, a sufficient coasting amount is secured for an outdoor running. Therefore, along with the possibility of a comfortable running on a level road, a steep uphill running is made easy, and the physical effort of the rider is alleviated.

An input device (such as a rotational hand crank) receives a constantly-applied motion, and outputs a signal to a controller which, in turn, sends an appropriate signal to an electric motor, which is connected to the chair via a mechanical transmission. The wheel is removably mounted in front of a wheelchair such that the front wheels of the chair are lifted above the ground. The device is generally steered manually, such as by pivoting an input device to one side.

A bar handle 5 is provided to extend from the rear parts of right and left side frames 3 and to form a gate shape in a double member structure made up of a fixed member 32 attached to the rear parts of the right and left side frames 3 and a movable member 33 disposed along at least upper side portion of the fixed member 33. A displacement detecting means 42 is interposed between the fixed member 32 and the movable member 33 to detect displacement of the movable member 33 relative to the fixed member 32. A control means is provided to control a driving motor so as to produce assisting power commensurate with the detected displacement.

A drive unit (54) for an electric motor-operated vehicle is provided with a planetary gear mechanism (58) having; a sun gear (58a) rotating together with a motor output shaft (57a), a planetary gear (58b) meshing the sun gear (58a), and a ring gear (58c) meshing the planetary gear (58b); and constituted that an arm plate (58d) supporting the planetary gear (58b) is rotated with the rotation of the motor (57) at a specified speed reduction ratio. The ring gear (58c) is supported for rotation relative to a housing and a switching mechanism (65) is provided to hold or release the relative rotation of the ring gear (58c).

A system and method for controlling a device such that device operates in a smooth manner. The system may switch between control architectures or vary gain coefficients used in a control loop to control the device. As the architecture or gains are switched, the control signal may be smoothed so that the device does not experience an abrupt change in the control signal it receives. In one embodiment, the control signal may be smoothed by adding a decaying offset value to the control signal to create a smoothed control signal that is applied to the device.