Technology

 E-dyn 96® Digital Displacement® pump

E-dyn® 96 Digital Displacement® pump

Highly controllable, and extremely efficient

animationMany of the vehicles and machines we rely on today are based on technologies developed more than a century ago.

Conventional hydraulic pumps – the core technology in many off-road vehicles – are controlled by changing the stroke of the piston with an analogue ‘swash plate’ mechanism, first patented in 1893.

This mechanism has a number of disadvantages – it is not easily controlled and there are many system energy losses, for example through idling, leakage and friction.

Our Digital Displacement® technology is a fundamental innovation. It utilises a radial piston machine which enables and disables cylinders in real time, using ultra-fast mechatronic valves controlled by an embedded computer.

These intelligent, digital controls mean an Artemis machine is highly controllable and extremely efficient – individual cylinders are only called into action as and when required. The net result is:

  • dramatically lower energy losses (typically less than a third of swashplate machines);
  • dramatically faster response (typically ten times faster);
  • complete elimination of high-frequency noise.

By replacing a mechanical device with one which is controlled by computer, new possibilities of system control, diagnostics and automation are enabled.

Our technology has real-life applications in off-road machinery, buses, trains and renewable energy.

For a full explanation of how our technology works, please download our technology overview (pdf).

Pump idle - 12ms - 320x320

Pump enabled - 12ms - 320x320

All six cylinders of one bank of a pump idling. The low-pressure valves above the cylinders are open and oil moves into and out of the cylinders at low pressure.  No work is done on the fluid and this is true even if the system pressure is at 420 bar.
When commanded to pump, the low-pressure valve above each cylinder closes as its respective piston reaches bottom-dead-centre.  This initiates the pumping stroke and the high-pressure valve opens to deliver oil to the external circuit.

Efficiency

Efficiency can be thought of as how much useful work gets done in comparison to the work wasted to machine losses.  Digital Displacement pumps reduce pressurised losses by selectively enabling cylinders to meet load demand.  In comparison to the swashplate mechanism, which cannot offload cylinders but instead reduces the stroke to reduce output, losses in the DD machine scale almost linearly with the amount of flow being produced.  In a swashplate pump, leakage and frictional losses cannot be avoided and a common method of improving efficiency is to reduce the shaft speed using a costly variable frequency drive.  Digital Displacement pumps achieve similar savings in terms of energy consumption but using conventional motors.

DDP 200 bar pressurised idle

Swash plate pump 200 bar pressurised idle

Digital Displacement Pump 200 bar pressurised idle
Swash plate pump 200 bar pressurised idle
Efficiency comparison of DDP and common swash-plate industrial pump

 

Control

Through the use of a solenoid valve on each piston, high bandwidth control over the pump output can be achieved. The decision to use a cylinder is made on a shaft turn by shaft turn basis in order to meet the pressure demand set in the pump controller.

Digital Displacement introduces a new concept to hydraulic pump control in the form of true pressurised idle.  With the shaft spinning and no demand to produce flow, all pistons are isolated from any line pressure and therefor incur minimal losses.  From the idle state, full flow can be achieved within 30ms independantly of working pressure.

Noise

Conventional hydraulic machines suffer from high radiated noise caused by port plate depressurisation.

This noise is pervasive and excludes hydraulics from some application areas such automotive or noise critital production or test environments.

Digital Displacement pumps don’t contain a port plate and compression energy in the cylinder is fully recovered before the low pressure valve poppet opens.

Benefits

  • Digital Displacement reduces losses by approximately 90% in comparison to a similarly sized axial piston pump
  • 30ms response time to demand, independent of pressure
  • Low investment in prime mover – induction motor plus soft starter / DOL
  • Reduction in fluid cooling requirement