Control of the supply pressure of a hydraulic actuator

A control device for controlling the hydraulic pressure of a hydraulic actuator of a transmission, said actuator including a cylinder and mating linings, comprising:

• a controller for producing a control signal having a first input for receiving an engine speed signal .omega..sub.m, a second input for receiving a turbine speed signal .omega..sub.t, a third input for receiving an engine load signal .alpha..sub.C, a fourth input for receiving a vehicle speed signal V.sub.v, a fifth input for receiving an enabling input E, and an output for transmitting said control signal;
• a pressure modulator connected to said output of said controller, said modulator being controlled by said control signal and closed by a lack of current on said output of said controller;
• said control signal being a function of the measurement of the slippage .DELTA..omega.=.omega..sub.m -.omega..sub.t when .alpha..sub.C and V.sub.v are less than preset threshold values, said control signal causing said pressure modulator to position said cylinder so that said linings mate;
• said controller including a first comparator and a second comparator, said first comparator comparing .DELTA..omega. to a first threshold .delta..omega. and said second comparator comparing .DELTA..omega. to a second threshold .epsilon.,
• whereby a large gain correction signal .delta.=.delta.(.DELTA..omega..sub.1) is generated to modify said control signal if .DELTA..omega..sub.1 =.delta..omega.-.DELTA..omega. is negative, a small gain correction signal .delta.=.delta.(.DELTA..omega..sub.2) is generated if .DELTA..omega..sub.1 is positive and .DELTA..omega..sub.2 =.epsilon.-.DELTA..omega. is negative, and a zero gain correction signal is generated if .DELTA..omega..sub.1 and .DELTA..omega..sub.2 are positive.