Design of mechatronic systems consisting of drive, control and non-uniformly geared transmissionsCopyright: © IGMR
Non-uniform transmissions in combination with controlled drives are used, for example, for motion tasks in which the temporal course of the output motion along the path curve is changed. In the case of fast-running transmissions with uneven transmissions and, in particular, those designed in a lightweight design to reduce drive power, the flexibility of individual components results in undesired vibration movement.
If high demands are placed on the accuracy of the movements, the output system must be extended by components for vibration reduction. These components contain, for example, model-based controls in which the motion errors due to the compliant components or the dynamic behaviour of the drives are taken into account. These are complex dynamic systems that have to be considered and designed as a whole. Within the framework of synthesis, the overall system is to be designed in such a way that the desired dynamic behaviour is achieved. This requires four steps:
- the synthesis of the output system consisting of an uneven transmission and drive motor,
- the analysis of the initial system and
- the synthesis of the regulator system
- the implementation of the controller system
Synthesis of the initial system
For the non-uniform transmission, a suitable transmission structure and the corresponding kinematic dimensions are determined within the framework of a structural and dimensional synthesis. Knowledge stores and synthesis programs are used here for example. Subsequently, the dimensioning of the components and the bearings is carried out. During the design phase, the freedom of play and stiffness of the components required for synthesis may not be guaranteed.
The synthesis of the drive is usually limited to the selection of a suitable motor, which fulfils the required speed and torque curves and also allows sufficient leeway for position intervention by the control system.
Analysis of the initial system
A good knowledge of the physical system as a whole in the form of physical and mathematical models is necessary for the targeted design of vibration reduction measures. For example, it provides information about
- the mechanisms of formation of oscillations.
- the feasibility of different vibration reduction measures.
- the necessary measured variables and actuators.
- the requirements placed on the actuators used to reduce vibration.
Synthesis of the regulator system
In order to improve the dynamic behaviour of the output system, to minimise unwanted vibrations, the output system must be extended by the additional components like actuators and controls for vibration reduction.
Implementation and testing of mitigation measures
Programs such as Matlab/Simulink can be used to implement the control concepts. In this case, the control system can first be created on a design computer and tested in a virtual environment, and then the control system can be ported directly to the hardware of a control computer.