Abstract: An object is displaced alternately in opposite directions, using a hydraulic power unit having a rotatable body which includes the shaft of a hydraulic machine having electronically commutated valves. A motor drives the rotatable body. The hydraulic machine drives an actuator to displace the object in use. Energy is transformed from rotational kinetic energy of the rotatable body to elastic strain energy or elastic strain and gravitational potential energy of the object during a pumping phase and rotation of the rotatable body slows, but does not change direction. The potential energy then drives the hydraulic machine to motor and the rotatable shaft speeds up again, storing rotational kinetic energy. The displacement of the hydraulic machine is controlled throughout to match a time varying demand taking into account the varying speed of rotation of the rotatable shaft. The motor provides energy to compensate for losses and the process can repeat cyclically.

Abstract: A measurement of the pressure of hydraulic fluid in a fluid working machine can be determined from the timing of the movement of valves which selectively seal a working chamber of cyclically varying volume from a fluid gallery. The timing of opening of a low pressure valve, to connect a working chamber to a low pressure fluid gallery, following the closure of a high pressure valve to seal a working chamber can be used to estimate the pressure in the high pressure fluid gallery at the moment of closure of the high pressure valve.

Abstract: A valve unit for a fluid working machine comprise a valve having a valve member (and optionally a valve seat), a valve actuator coupled to the valve member, and an electronic actuator controller which is integral to the valve unit and configured to actively control the valve actuator to thereby control the valve member.

Abstract: An object is displaced alternately in opposite directions, using a hydraulic power unit having a rotatable body which includes the shaft of a hydraulic machine having electronically commutated valves. A motor drives the rotatable body. The hydraulic machine drives an actuator to displace the object in use. Energy is transformed from rotational kinetic energy of the rotatable body to elastic strain energy or elastic strain and gravitational potential energy of the object during a pumping phase and rotation of the rotatable body slows, but does not change direction. The potential energy then drives the hydraulic machine to motor and the rotatable shaft speeds up again, storing rotational kinetic energy. The displacement of the hydraulic machine is controlled throughout to match a time varying demand taking into account the varying speed of rotation of the rotatable shaft. The motor provides energy to compensate for losses and the process can repeat cyclically.

Abstract: A measurement of the pressure of hydraulic fluid in a fluid working machine can be determined from the timing of the movement of valves which selectively seal a working chamber of cyclically varying volume from a fluid gallery. The timing of opening of a low pressure valve, to connect a working chamber to a low pressure fluid gallery, following the closure of a high pressure valve to seal a working chamber can be used to estimate the pressure in the high pressure fluid gallery at the moment of closure of the high pressure valve.

Abstract: A valve unit for a fluid working machine comprise a valve having a valve member (and optionally a valve seat), a valve actuator coupled to the valve member, and an electronic actuator controller which is integral to the valve unit and configured to actively control the valve actuator to thereby control the valve member.