A fluid system, comprising: a fluid-driven actuator; a pump that is fluidly connected to the fluid-driven actuator; an accumulator fluidly connected to the pump, the accumulator having, a shell that defines an interior volume, the shell including at least one port in fluid communication with the fluid system, an accumulator shaft disposed in the interior volume and extending at least partially across the interior volume from a first interior surface of the shell along a longitudinal axis of the shell, a piston-plate disposed in the interior volume such that the piston-plate and a second interior surface of the shell define a chamber in the interior volume, the chamber (19a,19b) in fluid communication with the fluid system via the at least one port, and a motor coupled to the piston-plate and having a shaft that interfaces to the accumulator shaft and having an outer radial surface that interfaces to an interior surface of the shell, a rotational movement of the motor translating to a linear movement of the piston-plate along the accumulator shaft such that a volume of the chamber (19a, 19b) varies based on a position of the piston-plate, a decreasing chamber volume injecting fluid into the system via the at least one port and an increasing chamber volume receiving fluid from the system via the at least one port for storage in the chamber (19a, 19b); and a controller that controls the motor to establish the position of the piston-plate along the accumulator shaft to control at least one of a magnitude, a direction and a duration of at least one of a pressure boost and a flow boost in the system, characterised in that: the motor is an outer-rotor type motor and the interface between the inner surface of the shell and the outer radial surface of the motor is a threaded interface. a fluid-driven actuator; a pump that is fluidly connected to the fluid-driven actuator; an accumulator fluidly connected to the pump, the accumulator having, a shell that defines an interior volume, the shell including at least one port in fluid communication with the fluid system, an accumulator shaft disposed in the interior volume and extending at least partially across the interior volume from a first interior surface of the shell along a longitudinal axis of the shell, a piston-plate disposed in the interior volume such that the piston-plate and a second interior surface of the shell define a chamber in the interior volume, the chamber (19a,19b) in fluid communication with the fluid system via the at least one port, and a motor coupled to the piston-plate and having a shaft that interfaces to the accumulator shaft and having an outer radial surface that interfaces to an interior surface of the shell, a rotational movement of the motor translating to a linear movement of the piston-plate along the accumulator shaft such that a volume of the chamber (19a, 19b) varies based on a position of the piston-plate, a decreasing chamber volume injecting fluid into the system via the at least one port and an increasing chamber volume receiving fluid from the system via the at least one port for storage in the chamber (19a, 19b); and a controller that controls the motor to establish the position of the piston-plate along the accumulator shaft to control at least one of a magnitude, a direction and a duration of at least one of a pressure boost and a flow boost in the system, characterised in that: the motor is an outer-rotor type motor and the interface between the inner surface of the shell and the outer radial surface of the motor is a threaded interface. a shell that defines an interior volume, the shell including at least one port in fluid communication with the fluid system, an accumulator shaft disposed in the interior volume and extending at least partially across the interior volume from a first interior surface of the shell along a longitudinal axis of the shell, a piston-plate disposed in the interior volume such that the piston-plate and a second interior surface of the shell define a chamber in the interior volume, the chamber (19a,19b) in fluid communication with the fluid system via the at least one port, and a motor coupled to the piston-plate and having a shaft that interfaces to the accumulator shaft and having an outer radial surface that interfaces to an interior surface of the shell, a rotational movement of the motor translating to a linear movement of the piston-plate along the accumulator shaft such that a volume of the chamber (19a, 19b) varies based on a position of the piston-plate, a decreasing chamber volume injecting fluid into the system via the at least one port and an increasing chamber volume receiving fluid from the system via the at least one port for storage in the chamber (19a, 19b); and a controller that controls the motor to establish the position of the piston-plate along the accumulator shaft to control at least one of a magnitude, a direction and a duration of at least one of a pressure boost and a flow boost in the system, characterised in that: the motor is an outer-rotor type motor and the interface between the inner surface of the shell and the outer radial surface of the motor is a threaded interface.