Applied Mechanics and Materials Vol. 307

Abstract: In this work, wear of reinforced poly-ether-ether-ketone (PEEK containing PTFE, graphite and carbon fibres) polymer bushes in friction against 7075 aluminium alloy cam plates is investigated in order to establish the application possibilities in transmission parts in humanoid robot joints. The PEEK bush surface conditions as well as the input axis-output axis transmission error (backlash) require close examination. Sliding wear tests were performed on bushes under 900 kgfcm loaded torque, while the cam plate oscillated. Based on the wear observation, it was found that PEEK wear fragments in the interface between PEEK bush and aluminium alloy cam plate formed a PEEK film.

Abstract: Because of the Limitations and shortcomings of the traditional multi-disciplinary optimization methods, this paper presents a useful optimal method named Analytical Target Cascading (ATC) for braking system characteristics optimization. The deceleration and pedal sense are chosen as the design targets. Brake system is divided into 4 subsystems: pedal, vacuum booster, master cylinder, brake. The optimization results show that ATC has a high degree of accuracy.

Abstract: Due to its simple structure, low consumption of energy but strong driving forces, Electrowetting on Dielectric (EWOD) is used most frequently in digital microfluidics for manipulation and control of droplets. In this paper, the internal mechanism of EWOD is explained though establishing the geometric model of unipolar board structure digital microfluidic chip. The digital simulation software COMSOL Multiphysics is applied to analyze the coupling fields. The results show that external flow velocity of micro-droplet is greater than the internal velocity. Based on the theoretic analysis, surface micromachining technologies are employed to fabricate the single-plate EWOD chip. Finally, an experiment platform is set up to test this chip. Experimental results show that 2μL droplet can be driven in velocity of 10cm/s and two droplets can be merged successfully. It will possibly provide an effective solution to the manipulation of droplets.

Abstract: Recent mechatronic systems, such as inspection machines or 3D imaging apparatuses, acquire and compute massive data for final results. A host in the mechatronic system is commonly composed of multiple hardware devices which interface with high-speed external signals. The host and the devices usually have large memory, so efficient data management is important due to data storage and transfer. In our software structure, each device is managed by respective application and large shared memory (LSM) is allocated in the host for the massive data. The shared memory is accessible from the device applications. Actions of the mechatronic system are driven by combining and broadcasting events through and inter-process communication (IPC). The model with LSM and IPC was applied to a 3D RF imaging system. We expect the proposed model can also be applied to machine vision with big image and engineering simulation with hardware accelerators.

Abstract: Mojette Transform (MOT) is used mainly in imaging implementation of mechatronicbased imaging system to reconstruct a discrete signal from a finite set of projection planes. The MOT uses a specific algorithm, called Corner Based Inversion (CBI), to reconstruct an image from its projections offering high-speed computing properties. Moreover, the MOT ensures a very low complexity in comparison to the reconstruction based on Fast Fourier Transform (FFT). In this paper, Graphic Processing Unit (GPU) based MOT is presented and also CPU and GPU processing are issued from 1283 image pixels. In the result, performance differences between the CPU and GPU architectures are discussed, and an approach of fast improvement in architectural efficiency is recommend.

Abstract: In order to improve the performance of sensorless PMSM control system, an improved sliding mode observer (SMO) is proposed in this paper. To decrease the vibration of SMO, a variable switching gain which changes according to the winding currentn is adopted. To improve the estimated value of rotor position, a extra low pass filter (LPF) is employed and the linear interpolation method is used to calculate compensation value of the phase delay caused by LPF. To verify the performance of proposed SMO, a sensorless field oriented vector control system of PMSM is designed. At last, the performance of the improved SMO and the sensorless PMSM vector control system are verified by experimental results.

Abstract: This paper presents a 3D piezoelectric ultrasonic motor using a single Flexural Vibration Ring Transducer. The motor consists of three main parts, the rotor, the stator and the housing unit. The stator is a piezoelectric transducer ring made from PZT S42 material. Three steel rods and a magnet were designed to support the rotor. The rotor is a sphere of metal that rests on the stator intersecting at the tips of the steel rods and the magnet. The housing unit is made of Perspex, a transparent thermoplastic material. Longitudinal and bending vibration modes, of oscillating structures are superimposed in the motor, generating elliptical micro motions at the driving tips. Pressing the rotor against the stator tips the micro motions are converted into a 3D rotational motion, via the friction between the tips of the three rods and the rotor. The motor structures, working principles, design and finite element analysis are discussed in this paper. A prototype of the motor was fabricated and its characteristics measured. Experimental tests show typical speed of movement equal to 35 revolutions per minute, a resolution of less than 5μm and maximum load of 3.5 Newton.

Abstract: This paper presents a standing wave rotary piezoelectric ultrasonic using a single flexural vibration transducer. The motor consists of three main parts, stator, rotor and housing unit. The stator is a single piezoceramic flexural vibration transducer. The rotor is made up of the motor driving wheel and the shaft. A computer simulation and modelling using finite element analysis for the proposed motor is discussed and used in the motor design development process. Finite element analysis has been used to evaluate the motor structure by performing an algebraic solution of a set of equations, describing an ideal model structure, with a finite number of variables. The established simulation and modelling for ultrasonic motor using finite element analysis enabled to select, the material of the flexural transducer, defining the operating parameters for the motor, determining the principles of motion and proposing an innovative technique to control the direction of motion, by controlling the phase between the two modes of vibrations. This enabled to create two directions of motion from a single vibration bar. A prototype of the proposed motor was fabricated and its characteristics measured. This showed that operating parameters of the fabricated prototype are: frequency equal to 40.7 KHz, voltage: 50: 100 volt and current: 50: 100 m-amperes. This is showed a close agreement with FEA. Typical output of the prototype is no-load speed of 120 rpm, a resolution on the order of micrometers and a dynamic response <100 µsec. The motor is able to carry a load equal to 2.8 Newton.

Abstract: Time-optimal controllers have been developed for mechatronic systems within the model predictive control framework (mpc). The time-optimal mpc controllers realize a minimization of the settling time for any given step reference by solving a constrained optimization problem. This allows to take into account system constraints as e.g. actuator limitations. One of the main challenges in this approach is solving the optimization problem within a few milliseconds such that sampling frequencies in the range of 100 hertz and more are feasible. These controllers are developed for applications which do not perform repetitive tasks but for which minimization of settling time is nevertheless crucial.