Locomotion Mechanism Of Micro Robot Based On Impact And Stick-Slip Driving

For their small sizes, high flexibility, and low manufacturing costs, micro and miniature robots have potential applications in many domains, such as, surface inspection, handling and assembly of MEMS (Micro-electro-mechanical systems), minimally invasive surgery, bio-engineering, and optical engineering, et al., The locomotion mechanisms in simple structures with high moving resolutions and high driving velocitys are required by the micro and miniature robots as they will handle with the sophisticated tasks. Unfortunately, the existing locomotion mechanisms cannot satisfy these requirements at the same time.To solve the problem mentioned above, a novel locomotion mechanism based on impact and stick-slip driving is proposed. Without any auxiliary transmission, the new locomotion mechanism, which is composed with integrated main body and some flexible driving legs, has a simple structure and is easy to be miniaturized. High moving resolution of less then 1μm can be achieved by the locomotion mechanism as the stick-slip driving principle is applied. At the same time, high locomotion velocity of more then 200mm/s can be obtained as the impact force driving principle in resonant state is applied. The conflict between high moving resolution and high driving velocity in a simple structure is solved by the proposed locomotion mechanism.Flexible leg is the basic unit of the mechanism, and the mechanism is driven by the vibration and the elastic deformation of the flexible legs. With the restriction of walking surface, the impacts between flexible legs and the walking surface is induced by the vibration, so, a vibro-impact system is constructed by flexible leg and walking surface. To simple the analysis, a multi-rigid-body model with finite degrees of freedom of the flexible leg is constructed based on the results of modal analysis and modal superposition theory to reduce the dimensions of system. Then, the impact model between the flexible leg and the walking surface is constructed based on Hertz contact theory and Coulomb friction theory. To measure the chang of motion parameters caused by impact, an experiment system is established, combining analysis and synthesis of the parameters, the parameters of impact model are identified.Stick-slip driving principle achieves a high moving resolution via switching the stick and the slip states between the mechanism and the walking surface by alternating the fast and the slow motion states. Stick-slip driving process is separated into stick phase and vibrating-slip phase, static analysis and transient dynamic analysis are performed to each pahse. Coupling between viberation and friction is studied numerically, and the relationship between the moving resolution and the driving voltage is analysised.Moviated by the sine signals with the designated frequency, the structure obtains a resonance state. Then the main body is driven with a high moving velocity by the impact between the legs and the walking surface, in which the impact is induced by the vibration of the flexible legs, as described above. The motions of the flexible leg are studied using the numerical simulation. The results show that the motions change from quasi-periodic to chaotic with the increasing of the leg amplitude. Poincarésection is established according to the moment when impact begins. By analyzing the distribution of the points in Poincarésection, the driving principle based on statistics rule of the impact force is discovered.A 70mm×35mm×15mm prototype with the weight of 3 gram is developed. The experimental system is established and its motion performance is tested. With the stick-slip driving principle, a moving resolution which is as high as 0.88μm is achieved. The relationship between moving resolution and driving voltage fit well with the analysis and the theoretic analysis results are well validated with the experimental results. With the impact force driving principle, a driving velocity reaches upto 280mm/s. The maximum driving velocity can be obtained when the driving frequency is 4.05KHz. The experimental results also agree with the theoretic analysis results. The measured impact time shows that the vibration of the flexible leg is in the chaotic state.