We present a hydro-elastic actuator that has a linear spring intentionally placed in series between the hydraulic piston and actuator output. The spring strain is measured for an accurate estimate of force. This measurement alone is used in PI feedback to control the force in the actuator. The spring allows for high force fidelity, good force control, minimum impedance, and large dynamic range. A third order linear actuator model is divided into two fundamental cases: fixed load-high force (forward transfer function), and free load-zero force (impedance). These two equations completely describe the linear characteristics of the actuator. This model is presented with dimensional analysis to allow for generalization. A prototype actuator that demonstrates force control and low impedance is also presented. Dynamic analysis of the prototype actuator correlates well with the linear mathematical model.

Force controllable hydro-elastic actuator

A stroke variable device comprising a large diameter cylinder and a small diameter cylinder which are interconnected to each other. A large diameter piston and a small diameter piston are slidably inserted into the large diameter cylinder and the small diameter cylinder, respectively, and a cylinder chamber is formed between the inner end of the large diameter piston and the inner end of the small diameter piston. A first seal member is arranged to surround the projecting outer end of the large diameter piston, and a second seal member is arranged to surround the projecting outer end of the small diameter piston. One end of the first seal member is fixed to the projecting outer end of the large diameter piston, and the other end thereof is fixed to the housing of the device to form a first hermetically sealed chamber therein. In addition, one end of the second seal member is fixed to the projecting outer end of the small diameter piston, and the other end thereof is fixed to the housing of the device to form a second hermetically sealed chamber therein. The cylinder chamber and both hermetically sealed chambers are filled with oil.

Device for varying a stroke

In a brake system for automotive vehicles comprising a master cylinder, wheel cylinders and a device for anti-lock control, the piston of the master cylinder is positioned in its nominal position by the variable volume of delivery of a pressure fluid source, in particular, a pump. The actual position of the piston is determined by a sensing device which is mounted on axially movable parts of the tandem master cylinder, booster, pedal assembly or other elements. The volume of delivery of the pump is adjusted so as to cause the piston of the master cylinder and, thus, the brake pedal to assume the desired position. For this purpose, the pump is connected with the pressure chamber of the master cylinder. Advantageously, it will be accomplished thereby that the brake pedal will not depress through its full travel when, during the control mode, more pressure fluid is removed from the hydraulic system, in particular from the pressure chamber of the master cylinder than the pressure fluid pump is able to deliver. Further, methods for monitoring the brake system with anti-lock control are provided wherein the sensing of the position, the direction of movement and/or the speed of the piston of the master cylinder are considered as an indicator for proper functioning of the anti-lock control device. This increases the safety of operation of the anti-lock device and its operating comfort.

Anti-lock brake system with variable delivery pump controlled in response to detected position of master cylinder piston and method therefor

An electromechanical motion amplifier in accordance with this invention is useful for controllably converting an input displacement into an amplified output displacement. This device comprises a first piston movable within a predetermined range of travel along an axis in response to the input displacement, and a second piston movable within a predetermined amplified range of travel along such axis. Force transmission means cooperating with the first and second pistons is utilized for effecting movement of the second piston in response to movement of the first piston. The relationship between the first and second pistons is such that movement of the first piston along the axis produces amplified movement of the second piston along the axis in a selected direction. In a preferred embodiment, the force transmission means is an elastomer, and the second piston is connected to a valve located in a nearby chamber, so as to directly control the positioning of the valve. The chamber is designed to contain a fluid under pressure, and the valve is designed to interact with a valve seat located on an outlet in the sidewall of the chamber. The positioning of the valve with respect to the valve seat thus serves to selectively control the flow of fluid out of the chamber.

Motion amplifier employing a dual piston arrangement

A brake control system in which the master cylinder has two pressurizing chambers for each brake circuit. Three brake circuits are disclosed in detail. One piston of each set of pressurizing chambers is directly applied by brake pedal force. The other piston of each set receives brake pedal force through resilient means, with additional force supplied by suitable servomotors. The servomotors are individually controlled to provide power-assist when appropriate, or to decrease the forces supplied by them to control wheel slip or wheel spin.

Power assisted braking system with wheel lock control

An electro-mechanical actuator for providing linear reciprocal motion which translates the short, abrupt linear stroke of a solenoid into a longer stroke of more uniform force on an actuating rod. The linear motion of the solenoid armature is coupled through a large spring adjacent a piston lying in a first chamber filled with a hydraulic fluid. A second chamber in communication with said first chamber houses a smaller diameter piston having an actuating rod disposed from one side. An accordion-like chamber adjacent the rod seal protects the seal from dust or damage.

Alvin S Blum

Papers

Electro-mechanical actuator