Real-time Control Unit Research Articles

Research on the Inverse Kinematics Prediction of a Soft Biomimetic Actuator via BP Neural Network

In this work, we address the inverse kinetics problem of motion planning of soft biomimetic actuators driven by three chambers. Soft biomimetic actuators have been applied in many applications owing to their intrinsic softness. Although a mathematical model can be derived to describe the inverse dynamics of this actuator, it is still not accurate to capture the nonlinearity and uncertainty of the material and the system. Besides, such a complex model is time-consuming, so it is not easy to apply in the real-time control unit. Therefore, developing a model-free approach in this area could be a new idea. To overcome these intrinsic problems, we propose a back-propagation (BP) neural network learning the inverse kinetics of the soft biomimetic actuator moving in three-dimensional space. After training with sample data, the BP neural network model can represent the relation between the manipulator tip position and the pressure applied to the chambers. The proposed algorithm is more precise than the analytical model. The results show that a desired terminal position can be achieved with a degree of accuracy of 2.46% relative average error with respect to the total actuator length.

Design and Construction of A Two Axes Sun Tracker Prototype with A Real Time Controller and Hybrid Stepper Motors (Dept.M)

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Software architecture for a multi-purpose real-time control unit for research purposes

A new, freely programmable, scalable control system for academic research purposes was developed. The intention was, to have a control unit capable of handling multiple PT1000 temperature sensors at reasonable accuracy and temperature range, as well as digital input signals and providing powerful output signals. To take full advantage of the system, control-loops are run in real time. The whole eight bit system with very limited memory runs independently of a personal computer. The two on board RS232 connectors allow to connect further units or to connect other equipment, as required in real time. This paper describes the software architecture for the third prototype that now provides stable measurements and an improvement in accuracy compared to the previous designs. As test case a thermal solar system to produce hot tap water and assist heating in a single-family house was implemented. The solar fluid pump was power-controlled and several temperatures at different points in the hydraulic system were measured and used in the control algorithms. The software architecture proved suitable to test several different control strategies and their corresponding algorithms for the thermal solar system.

The Rotating Erosion Testing Apparatus (RETA): A Laboratory Device for Measuring Erosion Rates versus Shear Stresses of Rock and Cohesive Materials

This paper describes an apparatus for testing the erosion rate of erodible rock and stiff clay as a function of water-flow-induced shear stress. The device, referred to as the Rotating Erosion Testing Apparatus, or RETA, is similar in design to other devices but has a number of advantages. The RETA uses a real-time control unit that monitors the shear stress via the torque imparted to the sample and adjusts its rotational speed to maintain a nearly constant shear stress throughout the test. RETA test results have been used to estimate local sediment erosion rates at structures founded in these types of bed materials.

Development of a real-time closed-loop micro-/nano-positioning system embedded with a capacitive sensor

The hysteresis and nonlinearity of the PZT is an actual problem in the piezo-driven micro-/nano-positioning stage, especially for the open-loop positioning stage. The study presents the development of an NI cRIO9074-based real-time closed-loop micro-/nano-positioning system, to overcome the problem of the hysteresis and nonlinearity of a PZT and to increase the positioning speed of the positioning stage. The developed system mainly consists of a piezoelectric actuator, a bridge-type hinge mechanism for displacement magnification, a micro-/nano-positioning stage body, a capacitive sensor system, an NI cRIO9074 real-time control unit with FPGA chip and a PC. After executing the optimization analysis of the displacement, stress and the frequency, using the ANSYS software, the dimensions of the stage body have been designed and determined. A set of software written with the LabView programming language was developed to construct the real-time PID closed-loop control of the developed positioning system. Based on the test results, the designed closed-loop micro-/nano-positioning system was capable of precision positioning within the travel of 119.08 µm with maximum stage tilting angle at 25 µrad. The steady-state positioning deviation of the stage is about ±2 nm in the step-positioning test. In the transient slope-tracing test at a tracing speed of 5 µm s−1, an error of about ±100 nm is observed.

Integrated force measurement for on-line cutting geometry inspection

A novel on-line cutting geometry inspection technique based on the integrated force-sensing method has been developed. A piezoelectric force sensor, mounted at the back of a single crystal diamond tool, was used to measure the cutting forces encountered by the tool system as it plunge-cut parallel micro flow channels on copper foils about 125 /spl mu/m in thickness. The force data were then converted by a software code which calculates the geometrical dimensions (depth and width) of the micro channels that had been cut. A series of experiments were conducted for four different feeds: 0.1, 0.3, 1.0, and 5.0 /spl mu/m/rev., at a constant workpiece speed of 2,400 rpm. Error analysis showed that the maximum relative error of the measurement, as compared to the results from the theoretical analysis, is 9.8%. By incorporating this force sensing technique into the machine tool control system, a real-time control unit can be implemented which conducts on-line adjustment of the diamond cutting performance to improve manufacturing quality.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>