IMPROVEMENTS IN ELECTRICALLY OPERATED DRIVE SYSTEMS

摘要

1,200,895. Control of two D.C. motors. SEVCON ENG. Ltd. and RANSOMES SIMS & JEFFERIES Ltd. 13 Nov., 1967 [14 Nov., 1966], No. 51010/66. Heading H2J. A vehicle is enabled to move along a curved path by varying the relation between the amounts of power supplied to two electric motors which are mounted on co-axial shafts coupled with respective driving wheels of the vehicle, each motor being supplied with intermittent current having a variable on-off ratio. A pulse generator is associated with each motor and controls the mean power derived through static switches from a D.C. source such as a battery. A differential unit accepts a variable amplitude signals from an accelerator unit and supplies the pulse generators with signals which depend upon the accelerator output voltage and the position of the steering mechanism. If this mechanism is adjusted to provide an amount of turn, one pulse generator receives a larger signal than the other in proportion to the amount of turn demanded. The accelerator unit comprises potentiometer VR1 with limiting resistor R1, transistors TR1, TR2, being supplied with common base potential from the wiper arm of the potentiometer. A potentiometer VR2 has its wiper arm mechanically coupled to the steering mechanism of the vehicle, the same signal being fed to both pulse generators A, B, when this arm is in midposition. Any displacement of the wiper arm from the mid-position of potentiometer VR2 will replace the signal to one side and increase it to the other. In a modification, the wiper arm of potentiometer VR2 is connected to the centre tap of the potentiometer resistor so that displacement of the arm reduces the input voltage to one of the pulse generators whilst the other input voltage remains constant. Adjustment of the steering mechanism thus reduces the power supplied to the motor which is inward with respect to the centre of curvature of vehicle path, the power supplied to the other motor remaining constant. The pulse generators may be controlled in accordance with the armature voltage of the motors. In another embodiment, the potentiometer VR2 is in the emitter circuit of the transistors TR1, TR2, the displacement of the wiper arm from the central position increasing the emitter current of one of the transistors whilst that of the other transistor remains constant. The transistors TR1, TR2, may be supplied from a high frequency source, the potentiometer VR2 being replaced by ganged capacitors linked with the steering mechanism and adapted for differential adjustment. Alternatively, inductor coils co-operate with ferrite rods linked with the steering mechanism. In other arrangements, the steering mechanism is associated with optical wedges associated with photo-cells, or a magnet coupled to the mechanism co-operates with Hall effect semiconductor devices.