Open hydraulic assistance system

A vehicle drive assistance system comprising an open hydraulic circuit comprising a hydraulic pump, a hydraulic motor and a reservoir, the hydraulic circuit comprising an intake duct connecting the reservoir to the hydraulic pump, a supply duct connecting the hydraulic pump to the hydraulic motor, and a return duct connecting the hydraulic motor to the reservoir,

• said vehicle drive assistance system further comprising a three-position valve connected to the supply duct and to the return duct, configured to, in a first position supplying the hydraulic motor in a first direction of operation, in a second position fluidly isolating the hydraulic motor from the hydraulic pump and connecting the hydraulic motor to the reservoir, and in a third position supplying the hydraulic motor in a second direction of operation opposite to the first direction of operation,
• wherein
• the hydraulic pump is a variable-displacement hydraulic pump, unidirectional, with displacement control slaved to a pressure setpoint;
• the vehicle drive assistance system comprises a flow controller valve positioned on the supply duct, between the hydraulic pump and the three-position valve, said flow controller valve being configured to, in a first configuration, prevent the passage of fluid through the supply duct of the hydraulic pump toward the three-position valve so that the displacement of the hydraulic pump is zero or is neutral, and in a second configuration, allowing the passage of fluid through the supply duct of the hydraulic pump toward the three-position valve, and
• wherein the three-position valve has:
• a first orifice connected to the hydraulic pump via the flow controller valve,
• a second orifice connected to the reservoir,
• a third orifice connected to a first orifice of the hydraulic motor,
• a fourth orifice connected to the reservoir, and
• a fifth orifice connected to a second orifice of the hydraulic motor,
• and wherein the second position connects the first orifice to the second orifice, and connects the third orifice to the fourth orifice and to the fifth orifice.