Browsing by Subject "Motion control devices."

Now showing 1 - 4 of 4

Open Access
Development of a modular control algorithm for high precision positioning systems
(2012) Ulu, Nurcan Geçer
In the last decade, micro/nano-technology has been improved significantly. Micro/nano-technology related products started to be used in consumer market in addition to their applications in the science and technology world. These developments resulted in a growing interest for high precision positioning systems since precision positioning is crucial for micro/nano-technology related applications. With the rise of more complex and advanced applications requiring smaller parts and higher precision performance, demand for new control techniques that can meet these expectations is increased. The goal of this work is developing a new control technique that can meet increased expectations of precision positioning systems. For this purpose, control of a modular multi-axis positioning system is studied in this thesis. The multiaxis precision positioning system is constructed by assembling modular single-axis stages. Therefore, a single-axis stage can be used in several configurations. Model parameters of a single-axis stage change depending on which axis it is used for. For this purpose, an iterative learning controller is designed to improve tracking performance of a modular single-axis stage to help modular sliders adapting to repeated disturbances and nonlinearities of the axis they are used for. When modular single-axis stages are assembled to form multi-axis systems, the interaction between the axes should be considered to operate stages simultaneously. In order to compensate for these interactions, a multi input multi output (MIMO) controller can be used such as cross-coupled controller (CCC). Cross-coupled controller examines the effects between axes by controlling the contour error resulting in an improved contour tracking. In this thesis, a controller featuring cross-coupled control and iterative learning control schemes is presented to improve contour and tracking accuracy at the same time. Instead of using the standard contour estimation technique proposed with the variable gain cross-coupled control, presented control design incorporates a computationally efficient contour estimation technique. In addition to that, implemented contour estimation technique makes the presented control scheme more suitable for arbitrary nonlinear contours and multi-axis systems. Also, using the zero-phase filtering based iterative learning control results in a practical design and an increased applicability to modular systems. Stability and convergence of the proposed controller has been shown with the necessary theoretical analysis. Effectiveness of the control design is verified with simulations and experiments on two-axis and three-axis positioning systems. The resulting controller is shown to achieve nanometer level contouring and tracking performance.
Open Access
Identification and stability analysis of periodic motions for a planar legged runner with a rigid body and a compliant leg
(2013) Bayır, Güneş
The Spring-Loaded Inverted Pendulum (SLIP) model is an extensively used and fundamental template for modeling human and animal locomotion. Despite its wide use, the SLIP is a very simple model and considering the effects of body dynamics only as a point mass. Although the assumption of a point mass for the upper body simplifies system dynamics, it prevents us from performing detailed analysis for more realistic robot platforms with upper trunks. Hence, we consider an extension to the classic SLIP model to include the upper body dynamics in order to better understand human and animal locomotion. Due to its coupled rotational dynamics, extending the SLIP model to the Body-Attached Spring-Loaded Inverted Pendulum (BA-SLIP) brings additional difficulties in the analysis process, making it more difficult to obtain analytical solutions. Consequently, simulations have been used to reveal the periodic structure behind locomotion with this model, and to find fixed points of discretized system dynamics. These fixed points correspond to periodic motions of the system and are important in designing controllers since they are used as steady-state control targets for most applications. The main concern of this thesis is to find fixed points of the BA-SLIP model and to investigate the dimension of the fixed point manifold. We performed extensive simulation studies to find fixed points of the system and the properties of the underlying space with a PD controller. Our simulations revealed the existence of periodic gaits, in which the upper body should be downward oriented for stable locomotion. Additionally, a region of stability is found such that the model sustains periodic gaits when it stays inside this region. Finally, we show that fixed points for running with upright body orientation are unstable when system dynamics are regulated with a constant parameter controller. We also present some simulation results which indicate the existence of stable periodic motions when controllers with time varying parameters, that use current state information, are used.
Open Access
Mechatronic design of a modular three-axis slider system for high-precision positioning applications
(2012) Ulu, Erva
Following the recent improvements in precision engineering related technology, interest for micro/nano-engineering applications are increased and various micro/nano-scale operations and products are developed. For micro/nano-scale applications, high-precision equipment including micro/nano-positioning devices with high accuracy and precision are required. In this thesis, mechatronic design of a three axes micro/nano-positioning device is discussed in detail. In order to satisfy nanometer level precision, an adaptive method to increase the available measurement resolution of quadrature encoders is presented. Performance characteristics of micro/nano-positioning devices usually include positioning accuracy of their each individual axis, operation range, maximum velocity and maximum acceleration. For this reason, permanent magnet linear motors (PMLM) are chosen as actuators in the presented design due to their outstanding characteristics. Moreover, in order to provide high-flexibility in terms of applications and simplify the control of the system, modularity is one of the main concerns while designing the micro/nano-positioning system presented here. Building the modular single axis slider system, three axes positioning device is constructed by assembling three of them perpendicularly. In this design, linear optical encoders are used as feedback sensors. Movement range of the designed system is 120mm in each direction. Since the available linear optical encoders have measurement resolution of 1µm, resolution of them is to be improved in software for sub-micron level positioning applications. For this purpose, a new method to increase the available measurement resolution of quadrature encoders is presented in this thesis. This method features an adaptive signal correction phase and an interpolation phase. Imperfections in the encoder signals including amplitude differences, mean offsets and quadrature phase shift errors are corrected by using recursive least squares (RLS) with exponential forgetting and resetting. Interpolation of the corrected signals is accomplished by a quick access look-up table calculated offline to satisfy linear mapping from available sinusoidal signals to higher order ones. With the conversion of the high-order sinusoids to binary pulses, position information is derived. By using the presented method, 10nm measurement resolution is achieved with an encoder with 1µm off-the-shelf resolution. Experiment results demonstrating the effectiveness of the proposed method are presented. Validation of the method is accomplished for several cases including the best resolution obtained. Practical constraints limiting the maximum interpolation number are also discussed in detail.
Open Access
Multi-sensor based ambient assisted living system
(2013) Yazar, Ahmet
An important goal of Ambient Assisted Living (AAL) research is to contribute to the quality of life of the elderly and handicapped people and help them to maintain an independent lifestyle with the use of sensors, signal processing and the available telecommunications infrastructure. From this perspective, detection of unusual human activities such as falling person detection has practical applications. In this thesis, a low-cost AAL system using vibration and passive infrared (PIR) sensors is proposed for falling person detection, human footstep detection, human motion detection, unusual inactivity detection, and indoor flooding detection applications. For the vibration sensor signal processing, various frequency analysis methods which consist of the discrete Fourier transform (DFT), mel-frequency cepstral coefficients (MFCC), discrete wavelet transform (DWT) with different filter-banks, dual-tree complex wavelet transform (DT-CWT), and single-tree complex wavelet transform (ST-CWT) are compared to each other to obtain the best possible classification result in our dataset. Adaptive-threshold based Markov model (MM) classifier is preferred for the human footstep detection. Vibration sensor based falling person detection system employs Euclidean distance and support vector machine (SVM) classifiers and these classifiers are compared to each other. PIR sensors are also used for falling person detection and this system employs two PIR sensors. To achieve the most reliable system, a multi-sensor based falling person detection system which employs one vibration and two PIR sensors is developed. PIR sensor based system has also the capability of detecting uncontrolled flames and this system is integrated to the overall system. The proposed AAL system works in real-time on a standard personal computer or chipKIT Uno32 microprocessors without computers. A network is setup for the communication of the Uno32 boards which are connected to different sensors. The main processor gives final decisions and emergency alarms are transmitted to outside of the smart home using the auto-dial alarm system via telephone lines. The resulting AAL system is a low-cost and privacy-friendly system thanks to the types of sensors used.