Patent ID: 6062332
Filing Date: 2000-05-16
Classification: B60K,B62D,F15B

Abstract:
A method of controlling a vehicle hydraulic drive system of the type comprising a source of pressurized fluid, a plurality of fluid pressure actuated motors connected in a parallel circuit with said fluid source; a driven wheel drivingly associated with each of said motors whereby said driven wheels are driven at varying speeds in response to varying rates of fluid flow to each of said motors; a source of control fluid pressure; each of said motors including an inlet conduit disposed upstream of said motor, and an outlet conduit disposed downstream of said motor when the vehicle is moving in a normal forward direction, the method being characterized by:(a) providing a proportional flow restrictor valve disposed in said outlet conduit of each of said plurality of motors;(b) determining the theoretical fluid flow for each of said motors, the cumulative theoretical flow for all of said motors, and the instantaneous theoretical fractional flow for each of said motors;(c) determining the actual fluid flow through each of said motors driving one of said driven wheels;(d) calculating a wheel flow error for each of said driven wheels representative of the difference between said theoretical fluid flow for each of said motors and said actual fluid flow through each of said motors; and(e) generating a pilot signal representative of said wheel flow error and transmitting said pilot signal to said restrictor valve, biasing said restrictor valve from a normal position providing generally unrestricted flow toward a flow restriction position.