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mechatronic system engineering

Internship: non-linear modelling of a High-performance lambda mechanism

Figure 1: Lambda mechanism (top view)

DEMCON is a company that develops advanced mechatronic systems for its customers. One of its recent developments is a so-called lambda mechanism that is able to drive and position an end-effector with high precision, see Figure 1. A simplified model is shown in Figure 2.

The lambda mechanism is actuated using two parallel ball screw drives. A ball screw drive translates rotational motion of a spindle to linear motion of a nut. Rotation of the nut is counteracted by linear guide rails with carriages. By varying the relative distance of the carriages, angle  can be controlled in such a way that the end-effector moves to any desired position in the -plane.

Figure 2: Simplified model

DEMCON has developed a linear dynamical model of the lambda mechanism by combining first-principles insights of the ball screws with modal analyses of the lambda arms. The model is used to design a suitable position controller using encoder feedback of the actuators ( and  in Figure 2) and feedforward control. Subsequently, a closed-loop time-domain simulation in Simulink® is performed to verify that the performance requirements are met.

During the development of the dynamical model, two challenges have come to light that require extra attention. The first challenge is related to the varying system dynamics along the range of motion of , see Figure 3. This non-linear effect is not captured in the current model. As such, it is not possible to perform reliable simulations of the lambda mechanism when  undergoes large rotations. The second challenge involves the connection of the ball screw sub-model with the sub-model of the lambda arms. Currently, several degrees-of-freedom are connected in Simulink® using manually tuned dampers and springs. This method adds additional states to the system and is prone to numerical instabilities.

Figure 3: Frequency response functions from T_1 to θ_1.

In this internship assignment, the goal is to develop a new, non-linear model, of the lambda mechanism that could be used for time-domain simulations with large angle displacements. First, a suitable modelling approach must be identified. Then the model should be built and compared to the existing solution. A time-domain simulation must be performed to verify that the performance requirements for large rotations of  are met. In the end, a report must be written according to academic standards.

Required pre-knowledge:

  • MSc program in Mechanical Engineering, Applied Mathematics, Electrical Engineering or Systems and Control, including courses related to control systems design for mechatronics, flexible multibody dynamics, system identification.

Acquisitie naar aanleiding van deze vacature wordt niet op prijs gesteld.

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