Continuous time controller based on SMC and disturbance observer for piezoelectric actuators

Abstract – In this work, analog application for the Sliding Mode Control (SMC) to piezoelectric actuators (PEA) is presented. DSP application of the algorithm suffers from ADC and DAC conversions and mainly faces limitations in sampling time interval. Moreover piezoelectric actuators are known to have very large bandwidth close to the DSP operation frequency. Therefore, with the direct analog application, improvement of the performance and high frequency operation are expected. Design of an appropriate SMC together with a disturbance observer is suggested to have continuous control output and related experimental results for position tracking are presented with comparison of DSP and analog control application

Analog controller based on sliding mode control for piezoelectric actuators

Today, the digital implementation of the controllers is mainly preferred from reprogrammability point of view. Many important control problems can be effectively solved using a digital architecture in conjunction with analog-to-digital (ADC) and/or digital-to-analog conversion (DAC). Digital solutions offer two very attractive advantages: (1)-promise to shorten design cycles, and (2)-provide the freedom to reprogram the design in simple ways. This ease-of-change stands in sharp contrast to the great effort required to redesign a typical hard-wired analog implementation. However, depending on the complexity of the plant and the degrees of freedom (DOF) to be controlled, digital implementation of an algorithm may be demanding due to the high computational power requirement to run in real time. The necessity for the acquisition of the analog signals on the other hand requires ADC and DAC conversions that compel extra conditions on the system. Hence, multi-DOF systems may require either diminish in the systems operation frequency or additional hardware to run the algorithm in parallel for each DOF. This work aims to develop an analog motion controller for single input single output (SISO) plants of complex nature. As the control algorithm, Sliding Mode Control (SMC) like the well known robust nonlinear controller is selected as a design framework. Originally designed as a system motion for dynamic systems whose essential open-loop behavior can be sufficiently modeled with ordinary differential equations, Sliding Mode Control (SMC) is one of the effective nonlinear robust control approaches that provide system invariance to uncertainties once the sliding mode motion is enforced in the system. An important aspect of sliding mode is the discontinuous nature of the control action, which switches between two values to move the system motion on so-called “sliding mode” that exist in a manifold and therefore often referred as variable structure control (VSC). The resulting feedback system is called variable structure system (VSS). The position tracking of the piezoelectric actuators (PEA) is selected as the test bed for the designed system. Piezoelectricity, the ability of the material to become strained due to an electric field, gives the possibility to user those materials as actuator in sub-micrometer domain for a range of applications. Piezoelectric effect is a crystalline effect, and therefore, piezoelectric actuators do not suffer from “stick slip” effect mainly caused by the friction between elements of a mechanical system. This property theoretically offers an unlimited resolution, and therefore piezoelectric actuators are already used in many applications to provide sub-micrometer resolution. Still the achievable resolution in practice can be limited by a number of other factors such as the piezo control amplifier (electronic noise), sensor (resolution, noise and mounting precision) and control electronics (noise and sensitivity to EMI). As a result of this work, we are aiming an analog controller for SISO systems and by the use of this controller, improvement on the tracking performance for the plant we are studying and decrease on the possible computational load on digital controllers is targeted

Realization of reactive control for multi purpose mobile agents

Mobile robots are built for different purposes, have different physical size, shape, mechanics and electronics. They are required to work in real-time, realize more than one goal simultaneously, hence to communicate and cooperate with other agents. The approach proposed in this paper for mobile robot control is reactive and has layered structure that supports multi sensor perception. Potential field method is implemented for both obstacle avoidance and goal tracking. However imaginary forces of the obstacles and of the goal point are separately treated, and then resulting behaviors are fused with the help of the geometry. Proposed control is tested on simulations where different scenarios are studied. Results have confirmed the high performance of the method

Piezoelektrik aktüatörler için analog kayan kipli denetleyici

Bu çalışmada Kayan Kipli Denetim (KKD) metodunun analog elektronikle uygulanması ve geliştirilen denetleyicinin piezoelektrik aktüatörlere uygulanması incelenmiştir. Sayısal uygulamalar öncelikle ADC ve DAC çeviricilerin yavaşlığı nedeniyle sınırlı hızlara erişebilirler. Öte yandan piezoelektrik aktüatörler neredeyse sayısal işlemcilerin çalışma frekansına yaklaşan yüksek rezonans frekansları ve sahip oldukları histerezis nedeniyle kontrolü güç, doğrusal olmayan sistemlerdir. Direk analog uygulama ile çalışma frekansında sınırlama olmadan performansın iyileştirilmesi beklenmektedir

Realization of reactive control for multi purpose mobile agents

The development of control method for an autonomous mobile robot that can be part of a multiagent system is the subject of this thesis. Mobile robots are built different purposes; for that reason, physical size, shape and mechanics, such as driving mechanism, of the robots would be very different. They are most of the time required to realize more than one goal at a time. Hence, as a minimum, required control must work in real-time and be able to respond to sudden changes that may occur in the environment. There is extensive research carried out, about autonomous mobile and stationaru robots, ranging from path planning and obstacle avoidance to multiple autonomous mobile robots. Proposed approach, for mobile robot control, is a layered structure and supports multi sensor perception. Each control layer uses only necessary sensor functions for its own process. Moreover, layers of control do not evaluate the signals to the necessary form asked by the layers. In this work, potential field method is implemented for obstacle avoidance. Unlike other solutions in the same framework, in this work assumed repulsive forces of the obstacles and attractive force of the goal point are treated separately. Then obstacles avoidance and goal tracking are fused in such a way that major drawbacks of the potential field method are overcome. Proposed control is tested on simulations where different scenarios are studied. The simulation results confirmed the high performance of the method. The proposed control is a potential alternative for mobile robots control operating in dynamic environments and as an agent in a multiagent syste

Control of piezoelectric actuators using analog sliding mode controller

In this work, an analog application for the sliding mode control (SMC) of piezoelectric actuators (PEA) using FPAA is presented. Applied SMC is known to have order of sampling time square tracking error. DSP application of the algorithm suffers from ADC and DAC conversions and faces speed limitations. Moreover PEA is known to have very large bandwidth close to the DSP operation frequency. Therefore, with the direct analog application, improvement of the performance is expected and high frequency operation will be achieved. Experimental results for position tracking using DSP and analog application are presented

Sliding mode based obstacle avoidance and target tracking for mobile robots

In this work, we suggested a solution for the basic tasks of a mobile robot capable of being a building block of an intelligent agent in group. This solution includes obstacle avoidance and goal tracking implemented as two different controllers. A geometry based behavior arbitration is proposed for fusing the output of those two controllers. Proposed structure is tested both on simulations and on real robot with different scenarios. Results have confirmed the high performance of the method