Abstract: A variable capacitor whose capacitance is a function of shaft position is coupled to a rotating shaft. A constant voltage is applied to the capacitor. As the shaft rotates, the changing capacitance of the variable capacitance causes current to flow into and out of the variable capacitor in response to the shaft rotation--thus providing a current source with no inherent practical frequency response limitations. A transresistance amplifier converts the current to an output voltage which is proportional to instantaneous shaft velocity. Various arrangements are used to eliminate the discontinuity associated with the inherent sign change of the capacitance time derivative while retaining the signal components associated with instantaneous velocity changes of the rotating shaft.

Abstract: An electric control is disclosed for an electrically powered vehicle having independently controlled left and right drive motors and associated drive wheels to propel and steer the vehicle. The electrical control includes left and right closed loop control circuits for respectively accelerating either or both of the drive wheels whenever a speed command or error signal associated with such drive wheel exceeds a first determined value. Dynamic braking is provided by connecting in parallel electrical relationship an associated brake resistor across one or both of the motors whenever the speed command signal associated with such motor does not exceed a second predetermined value.

Abstract: A collapsible portable manual wheel chair is converted to a collapsible electric wheel chair. The two large rear wheels of the collapsible manual wheel chair are removed, and an electromechanical drive unit is substituted in their place. The drive unit includes a left drive wheel assembly, a right drive wheel assembly, a battery mounting assembly, and a control device supplying electric power to each of the drive wheel assemblies for propelling and steering the wheel chair. The left and right drive wheel assemblies and the battery carrier assembly are each manually removable from the wheel chair frame to permit collapsing the wheel chair frame and are each manually removable from one another to provide portable light weight components.