Method for estimating pressure in a pressure actuated controller

A method for estimating brake pressure in a hydraulic control system having fluid pressure-operated elements, each of said pressure-operated elements having a fluid pressure working chamber, a pressure supply line and a pressure fluid return line communicating with said pressure working chamber, a solenoid operated pressure build valve means in said supply line defining a controlled restriction in said pressure supply line, a solenoid operated pressure dump valve means in said pressure fluid return line communicating with said pressure working chamber for establishing a controlled flow restriction between said pressure working chambers and an exhaust region, said method including the steps of:

• commanding a solenoid duty cycle for said pressure build valve means to establish a controlled flow restriction in the supply line for said working pressure chamber;
• commanding a solenoid duty cycle for said dump valve means to establish a controlled flow restriction between the flow outlet side of said build valve means and said exhaust region;
• detecting a pressure differential between supply pressure in said supply line and pressure on the flow outlet side of said build valve means;
• detecting a pressure differential between brake pressure on the flow outlet side of said fill valve means and the flow outlet pressure in said exhaust region;
• and
• calculating flow into and out of said build valve means and said dump valve means in accordance with a functional relationship between integrated differential flows and said brake pressure.