A palm unit for an artificial hand comprises: a palm unit body (70)； a motor (68) held by the palm unit body (70)； a hydraulic pump assembly (72) held by the palm unit body (70) and comprising a low-pressure hydraulic pump (76) and a high-pressure hydraulic pump (74), wherein both hydraulic pumps (74, 76) are powered simultaneously by the motor (68)； and a hydraulic circuit held by the palm unit body (70) and coupled to both hydraulic pumps (74, 76), wherein the hydraulic circuit has a low-pressure configuration in which the discharge sides of both hydraulic pumps (74, 76) a re coupled to one or more hydraulic actuator(s) (36, 38) for the artificial hand and a high-pressure configuration in which the discharge side of the low-pressure pump (76) is isolated from the hydraulic actuator(s) (36, 38) and recirculates fluid to the suction side of the low pressure pump (76) with the discharge side of the high-pressure pump (74) remaining coupled to the hydraulic actuator(s) (36, 38), and wherein the hydraulic circuit is arranged to switch from the low-pressure configuration to the high-pressure configuration automatically during a closing grip pattern when the pressure in the system increases beyond a threshold value.
