Hydrostatic power steering system having reduced wheel slip

A hydrostatic power steering system comprising a source of pressurized fluid, a fluid pressure actuated device including means operable to indicate steered wheel position, a fluid controller operated by means of a steering input device, and being in fluid communication with said source of pressurized fluid, by means of a fluid supply passage and with said fluid pressure actuated device by means of a high pressure path and a low pressure path;

• said fluid controller including means operable to indicate steering device position, control logic operable to compare said steered wheel position and said steering device position and to generate an error signal representative of the difference therebetween;
• characterized by:
• (a) said source of pressurized fluid including means operable to generate an additional path of pressurized fluid, at a pressure somewhat greater than the fluid pressure in said high pressure path;
• (b) valve means in fluid communication between said additional path of pressurized fluid and said high pressure path, and operable between a first position blocking fluid communication and a second position permitting fluid communication;
• and
• (c) said control logic including means operable to determine when said steered wheel position approaches a predetermined position, and when said error signal approaches zero, and to generate a command signal to said valve means to move said valve means toward said second position, whereby said additional path of pressurized fluid is in communication with said high pressure path, substantially preventing further movement of said steering input device, and maintaining said error signal at approximately zero.