Search results

Economic, flexible and efficient micro production needs new miniaturized automation equipment (desktop factories). Micro assembly processes make demands on precision of miniaturized robots used in desktop factories and the driving concepts, as well as miniaturized machine elements. The purpose of this paper is to investigate miniaturized drives using micro harmonic drive gears, which are promising driving concepts.

The analysis of the miniaturized precision robot Parvus (using micro harmonic drive gears) shows a good repeatability but also room for improvement concerning the path accuracy. Thereby the transmission error of the micro gears is identified as main disturbing influence concerning the robot's precision characteristics. Owing to the size reduction of the micro harmonic drive gear and the slightly different working principle compared to larger harmonic drive gears, the transmission error are more pronounced. Therefore, it is necessary to discuss approaches to compensate for this effect.

A very promising approach is the use of a simplified model of the kinematic error within the robot control to compensate for this disturbing effect. Measurement data of the transmission error is mathematically transformed into the frequency domain and filtered to the most important frequency modes of the function. These modes are used to build up a simplified mathematic model of the gear transmission error. A final test using this model as compensation function demonstrates that it is possible to reduce the transmission error of the micro gears by more than 50 percent.

The paper presents the first investigation into compensation of the transmission error of micro harmonic drive gears.

Until now, the size range of most machines for precision assembly was much larger than the size of the pieces to be handled or the necessary workspace. Flexibly scalable miniaturised production machines can help to develop much more flexible micro production systems. The paper aims to describe the development of a micro‐parallel‐SCARA robot adapted in size to MEMS products.

The robot consists of a miniaturised parallel structure, which provides a high level of accuracy in a workspace of 60 × 45 × 20 mm³. It has a base area of 130 × 170 mm² and offers four degrees of freedom.

Based on simulations, the degree of miniaturisation in terms of a smaller structure and a high level of accuracy is determined. The results show that a miniaturised hybrid robot with a plane parallel structure driven by miniaturised zero‐backlash gears and electric motors can reach a theoretical repeatability better than 1 μm.

The first prototype provides good prospects that the concept will be used in a visionary desktop‐factory. As regards the accuracy parameters of the robot, there will be further efforts to optimise the robot's structure and drive mechanism.

The repeatability of this first prototype is better than 14 μm. A better stiffness of optimised micro‐gears and joints of the structure will guarantee a much better repeatability.

The paper illustrates that the Parvus is one of the smallest industrial robots for micro assembly equipped with a full range of functionalities like conventional industrial robots.