Fluid Power Laboratory

The Fluid Power Laboratory comprises a number of different test set-ups ranging from small custom set-ups to the world’s first full scale wave simulator test-bench, designed for testing Power Take Off (PTO)-systems for wave energy converters.

The laboratory facilities include:

  • Hydraulic power supplies

         1. 325 kW hydraulic power supply
         2. 110 kW hydraulic power supply
         3. Several minor and medium sized power supplies (5-40 kW)
  • Full scale wave simulator test bench
  • Brake stand for wind turbine transmission
  • Hydraulic servo robot
  • HMF-680 mobile hydraulic crane
  • Small scale cranes for testing control strategies
  • Custom set-ups for testing components
  • State-of-the-art measurement equipment and transducers

Test Facilities at collaboration partners

Besides the laboratory facilities at the university, the industry partners provide test facilities that are available for experiments supporting the work in the research project. These test facilities a full scale pitch stand and full scale hydraulic yaw test stand at Hydratech Industries in Silkeborg and the full scale Wave Star prototype WEC at Hanstholm.

Full scale hydraulic yaw system and test stand available for testing at Hydratech Industries.

Full Scale Wave Simulator Test Bench

The laboratory includes the world’s first full scale wave simulator testbench, designed for testing Power Take Off (PTO)-systems for wave energy converters. The testbench consists of two cylinders mounted back-to-back, where first cylinder (wave cylinder) emulates the waves and the inertia of the float and the second cylinder, which is a special multi-chamber cylinder is part of the PTO-system under test.
The system is able to produce forces of more than 800 kN at velocities up to 1 m/ and is fully equipped with state of the art transducers for measuring all states in the system. The testbench will be used to analyse, optimise and compare different PTO-systems and for developing new control strategies for wave energy systems. A further description of the wave simulator may be found here.

The full scale wave simulator test bench used for testing PTO-concepts and control strategies.

325 kW Hydraulic Power Supply

The laboratory comprises a number of hydraulic power supplies, with the largest being 325 kW. The power supply consists of two pumps (250 ccm/rev and 125 ccm/rev) which may be run in parallel or individually. Running in parallel the pumps are able to deliver a continuous flow of more than 500 l/min at 350 Bar operating pressure, and using the installed accumulators the flow may reach more than 800 l/min for short periods of time.

325kW Hydraulic power supply.

Brake stand for wind turbine transmission

To test braking strategies for a wind turbine, a small scale version of the main shaft in a wind turbine transmission is available. The set-up is designed to show the same dynamic behaviour as a real transmission with regard to torsional oscillations in the system in terms of both frequency and relative amplitudes. The system consists of the main shaft connected with a flywheel and a disc brake through flexible clutches, which are matched to yield the same oscillations as seen in real turbine shaft. The system is fitted with transducers to measure the torsional strain in the main shaft, rotational speed and brake pressure.

Stand for testing braking strategies for wind turbines.

Hydraulic servo robot

A two-d.o.f. custom made hydraulic servo robot is installed in the laboratory and is used as test object for testing new and advanced control strategies for both single cylinder control and tool centre control. The robot is fitted with high performance servo valves and specially designed made low friction cylinders to obtain the most well defined system with a high bandwidth. As the two axes are highly coupled, one axis may be used as (a well defined dynamic) disturbance while operating the other, hence making a great object for e.g. testing robustness of different controllers. The robot is fitted with pressure and position transducers, along with an accelerometer at the tool centre.

Hydraulic servo robot

HMF-680 mobile hydraulic crane

A full featured HMF-680 mobile hydraulic crane is available for testing. The crane has three degrees of freedom, including a four link telescopic arm, which gives the crane a total reaching capacity of approximately 10 meters. In the fully extended situation the crane is capable of carrying a load of more than 400 kg. The crane is fully equipped with strain gauges in all critical places, position measurement at individual joints and pressure and flow transducers. Besides this it is possible to measure the Tool Center (TC) position allowing for both TC control and dealing with the flexibility in the mechanical structure. The crane is used for both research and student projects.

325kW Hydraulic power supply

Small scale cranes for testing control strategies

Three small scale versions of cranes are available as loads or test objects, when e.g. testing control strategies in combination with over-centre valves. The cranes all have well defined loads and are completely fitted with flow, pressure and position transducers along with strain gauge measurements at selected places. The cranes are furthermore used as basis for student projects.

Example of small scale cranes found in the laboratory

Custom set-ups for testing components

When it comes to e.g. components testing, most of the experiments are made using custom set-ups designed for the particular component or system in question. The laboratory has a large number of different valves, hoses, accumulators etc. on the shelves making it possible to design specific set-ups for the experiments required. The laboratory furthermore benefits of having access to in-house fully equipped mechanical and electronic workshops which can manufacture parts and components required in the laboratory. An example of a custom set-up is the 1 cylinder prototype of a digital displacement pump, shown in the below pictures. The pump and set-up is made fully in house including all mechanical parts and the electronics controlling the pump.

Prototype of digital displacement pump with custom set-up for measuring all states in the system

State-of-the-Art Measurement Equipment and Transducers

The laboratory is very well equipped with state of the art in transducers and measurement equipment, including but not limited to:

  • VSE RS800/50 flow meters which dynamically can measure flows up to 800 l/min
  • Parker SCQ 60 and 150 l/min versions transient response time in the ms-range
  • Danfoss MSB and HBM pressure transducers in all ranges up to 600 Bar operating pressure
  • A variety of different position transducers, tachometers, accelerometers and torque transducers
  • Strain gauge amplifiers and inductive transfer systems for strain gauges
  • NI data acquisition and real-time systems (Compact Rio and real-time PCs)
  • DSP and xPC based solutions for data acquisition and real-time control