Emphasis in our research is given to the development and investigation of new concepts for oil hydraulic drives. These drives are essential where high power density and fast dynamics are necessary. They put a heavy burden on control and measurement, thus being a truly mechatronics related field.
Currently both projects together with industrial companies as well as long term fundamental research are carried out. The first emphasize the investigation of complex problems in drive technology, where there is a high demand for industrially applicable solutions which can be implemented easily into real world plants and machinery. Our fundamental research focuses on the future of oil hydraulics:

• Energy efficient switching techniques in hydraulic drives
• Application of nonlinear control techniques to the hydraulic linear drive
• Development of high speed switching valves
• Integration of Microcontrollers in Hydraulic Drives

The next paragraphs give you some introductory information on some of our research projects.

• LCM GmbH:
  • A hydraulic Variable Valve Train
  • Automatic Level Control System for Pick-up Devices
  • Sheet bending with innovative press-brakes
  • Handling Complexity
  • Dynamics and Control of Switching Systems
• BOSCH Rexroth AG:
• Energy Efficient Control Techniques for Oil Hydraulic Drives
• Drive Problems in a Stainless Steel Rolling Mill
• VOEST-ALPINE Industrieanlagenbau GmbH:
• Linear Drive Problems
• Compact Oscillatory Drive for a Continuous Casting Unit
• Additional projects:
• Investigation of Hydraulic Servo Valves

Partner companies: , ,
Inlet and outlet valves of combustion engines classically are actuated by means of a cam-shaft. However, the camshaft is at its technical limits w.r.t. the speed of motion and its possibilities to change the timing and duration of the valve opening within preferable ranges.
It is well known that a fully variable valve train, capable of going beyond the limits of the cam-shaft, offers a decisive performance potential w.r.t to fuel consumption and operational flexibility for many combustion engines.
An new actuation principle was developed which exploits a hydraulic spring concept. Chambers filled with compressed oil are connected with the two sides of a hydraulic piston forming in this way a spring mass oscillator. Basically, the motion is controlled by a fast hydraulic valve which connects or disconnects the hydraulic line between one chamber and one piston side. Auxiliary valves refill energy lost by dissipation and take care that the motor valves attain correct starting positions.
Most challenging development tasks have been: the development of fast switching valves and the proper dimensioning of the hydraulic circuitry. The very fast processes (only a few milliseconds) make the dynamic effects in the hydraulic system a crucial part for proper functioning.

A prototype has been developed and successfully cold tested.

Partner companies: , ,
Mechatronic concepts are currently getting more and more important in agricultural machinery. They are already reality in tractors and autonomous harvesters. For implements like plows, mowing devices, sowing machines, or harvesters for grass or hay, "mechatronization" is right at its beginning.
The general requirements of agricultural machinery to mechatronics are quite challenging: Higher functionality must result in more throughput by more accurate and faster operation and ease of use needs to be improved as well. Increase of costs on the customer side, both in price and in maintenance must be kept extremely low.

Objectives
This is a key project by means of which most relevant functions are studied and solutions are developed for. These functions are

• A fast response, robust and cheap actuation device: hydraulic meets the requirements best but novel concepts must be developed to achieve fast response at low costs
• Low cost distance sensors to measure distance to ground: is a key technology for realizing mechatronic concepts for this kind of machinery with a wide range of applications; wanted is a system to screen reliably and fast the ground profile even underneath agricultural goods such as grass, hay, etc.
• Low cost electronics by combining state of the art micro-controllers with proper power electronics to link sensors to actuators and to communicate with the tractor's electronics and the driver

Results obtained hitherto
In the project the following topics have been addressed and results were obtained respectively: A hydraulic actuator based on low cost proportional valve technology was successfully developed and tested.
Radar and ultrasonic distance sensors have been examined with respect to the requirements. There are severe difficulties to sense ground through the swath. Solutions for that need further basic research. Ultrasonic sensors are able to detect ground outside of the swath.
Successful field tests
The basic functionality was proven by means of a prototype comprising two ultrasonic sensors, a micro-controller, and low cost proportional hydraulics in field tests.
Switching control
Currently, work is focussing on even cheaper and more robust hydraulic actuators using switching techniques. For this purpose, fast and cheap switching valves are developed.

Partner company: ,
The drive and its role
The drive system of a press-brake decisively influences the quality of the product and the operating efficiency: Close product tolerances ask for a precisely controlled press actuation, maximum operating efficiency needs minimum cycle periods and low energy consumption. In addition to all this, the production costs for the press-brake must be kept as low as possible.
Development project
The drive system of a hydraulic press comprises the hydraulic power unit and the electronic control system. In this project, development for both systems is done addressing novel concepts as well as some novel components, such as specific hydraulic valves.
Development methods
We make extensive use of mathematical modeling and simulation to evaluate new ideas, prior to the detail design and manufacturing. This saves cost and development time. Experimental verification in the hydraulic laboratory of the final design of components as well as of the whole drive systems is a must. A further focus is control of the hydraulic system. Controller design, simulation and experimental tests are facilitated by modern and powerful development tools. These enable rapid modification of controller concepts or parameters respectively which leads to optimized final results.

Partner company: ,

Complexity
The functionality of modern products increases and with it also complexity. Increasing complexity reduces probability of successful development, production, start-up, and maintenance. Hence, complexity must be understood and controlled.
Complexity measures
The first part of this project was to find applicable complexity measures. Complexity of a product or system depends on the observer's perspective. New complexity measures have been developed for the purpose of concept evaluation. They operate on an abstract functional as well as on the technical level. The mathematical consistency and technical usefulness of the proposed measures has been demonstrated by a few examples.
Design Methods and Complexity
The selection of the best fitting design method and its support with modern 3D-CAD systems is a promising way to control complexity. For the concept of variant design, which is essential in metallurgic machinery, an algorithm for the selection of the design concept has been created and tested by a few examples, Attention was paid particularly to the choice of optimal design parameters.

Partner company:
As opposed to resistance control, hydraulic switching control promises high efficiency and low actuator cost. Fast switching valves as well as measures for decoupling the pulsations caused by these valves are required. Two different prototypes of fast switching valves have been designed and are currently tested. A decoupling system has been implemented on a test stand.

Partner companies:

Aim of these projects is to adapt switching techniques (similar to the technologies utilised in power electronics) to hydraulic drives. The following two new methods have been developed and patents have been granted:

• Wave Converter: Oscillations in an oil colomn are excited by periodically switching valves which yield a controlled pressure at the output port.
• Resonance Converter (prototype is shown on the right): A spring-mass oscillator acts as a short time energy storage medium. This method controls the output flow rate and thus can be easily applied to velocity control of drives.

Partner company: ,

The hydraulic drive of a rolling mill showed operating states where the drive pumps broke down. A detailed modelling and simulation of the relevant section of the plant helped to identify the reason for this failure and the development of proper countermeasures. After putting the proposed modifications into practice, no more failures occured.

Partner company:
The Department is equipped with a hydraulic linear drive unit where several problems occurring in practical drives can be simulated and solved. Here are a few examples:

• Development of a thickness adjusting mechanism for a continuos cast plant (in cooperation with VÖEST-Alpine Industrieanlagenbau).

• Application of the singular perturbation theory to simplify the model equations of a servo drive. Design of new nonlinear controllers and comparison with other state-of-the-art controller types.

Partner company:
Aim of this work was to come up with a new design for the drive and the suspension of a continuous casting mold. A major demand was low cost of maintenance. One new feature of this design is an elastic suspension without conventional bearings where previous plants showed high wear and probability of failure.

To be able to model and simulate hydraulic drives accurately, one needs to have solid knowledge of its components. To gather this knowledge, several commonly used components are investigated in both theory and experiments and the results are compared.

The picture on the right shows the measurement of the characteristics of the so-called torque motor which is the primary control element in a servo valve.

This valve family is the most accurate and fastest linear type available.