Design of a Sliding Mode Controller with Fuzzy Rules for a 4-DoF Service Robot

In this study, a novel control strategy that combines a fuzzy system and the sliding mode controller is proposed for improving stability and achieving high-accuracy control in service robots. Based on the kinematic and dynamic models of a 4-degrees of freedom manipulator, and the observed tracking error using a low-cost inertial sensor, the proposed fuzzy sliding mode controller (FSMC(IMU)) is designed to generate appropriate torques at robot joints. The FSMC(IMU) controller parameters are adjusted through a fuzzy rule that determines the state of the system. The error in trajectory tracking is reduced through this. The gain value K can be finely adjusted by fuzzy control by observing the degree of vibration after entering the sliding mode surface. The larger the observed vibration value, the faster the fuzzy controller follows the given input trajectory by selecting a smaller gain value K and reducing jitter due to the sliding mode control’s discontinuous switch characteristics. When the degree of error is small, it achieves faster and more accurate control performance than when the observer is not used. The stability of the FSMC(IMU) system is verified via disturbance experiments. The experimental data are compared with the conventional sliding mode controller and proportional-derivative control. The experimental results demonstrate that the proposed FSMC(IMU) controller is stable, fast, and highly accurate in controlling service robots.

     

Obstacle recognition using a haptic device

A haptic device is proposed which gives the user feedback information on their location and orientation of the obstacle through the mobile robot that detects the obstacle in an environment where the user cannot see.Mobile robot recognizes the exact position of the obstacle through configuring the nested ultrasonic sensor and giving feedback information to the haptic device.The haptic device consisting of five vibration motors can realize the haptic through the vibration of user＇s finger using the position information of the obstacle received feedback.In addition,it has high accuracy to recognize the surrounding environment and realizes the various situations with the fuzzy controller and the nested ultrasonic sensors.     

The Tracking of a Moving Object by a Mobile Robot Following the Object’s Sound

The tracking of a moving object with a mobile robot has been implemented based on the detected sound from the moving object using a microphone array. The difference between the travel times of the sound source to each of the three microphones mounted to the robot has been used to calculate the distance and orientation of the sound source. The cross-correlations between the received signals have been used to detect the individual sound signal from the object and to calculate the time difference between two signals. This provides reliable and precise time differences among the sound signals arrived at the microphones compared to the conventional method. In order to determine the tracking direction to the sound source, Fuzzy rules have been applied; the results are used for real-time control of the mobile robot. The efficiency of the proposed algorithm has been demonstrated through real-world experiments and compared to the conventional approach.     

Adaptive Fuzzy Super-twisting Backstepping Control Design for MIMO Nonlinear Strict Feedback Systems

International Journal of Control, Automation and Systems - This paper presents a new backstepping control (BSC) combined with a super-twisting algorithm (STA) for multiple-input, multiple-output...     

Outdoor position estimation based on a combination system of GPS-INS by using UPF

This paper proposes a technique that global positioning system(GPS)combines inertial navigation system(INS)by using unscented particle filter(UPF)to estimate the exact outdoor position.This system can make up for the weak point on position estimation by the merits of GPS and INS.In general,extended Kalman filter(EKF)has been widely used in order to combine GPS with INS.However,UPF can get the position more accurately and correctly than EKF when it is applied to real-system included non-linear,irregular distribution errors.In this paper,the accuracy of UPF is proved through the simulation experiment,using the virtual-data needed for the test.     

Static attitude control for underwater robots using multiple ballast tanks

A new dynamic control scheme that uses the center of gravity is proposed to control the attitude of an underwater robot. Instead of using thrusters, ballast tanks are used for the static attitude control to avoid generating disturbances around the robot and to lower the power consumption. Five attitude ballast tanks are used to control the roll and pitch of the robot via the translocation of water. Using the dynamic center of gravity, the attitude can be maintained and controlled at a desired angle. The dynamics of the robot are derived using Lagrangian equations. By using the dynamic equations to find the optimal gains of the Proportional Derivative (PD) controller, this robot has been designed to have a fast attitude control capability with low power consumption. Through real experiments, it is demonstrated that the attitude control is efficient and accurate by adjusting the center of gravity. It is also verified that this system has outstanding efficiency in power consumption compared to conventional propeller systems. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Study on denoising filter of underwater vehicle using DWT

In the step processing a digitalized signal,noises are generated by internal or external causes of the system.In order to eliminate these noises,various methods are researched.Among these noise elimination methods,Fourier fast transform （FFT） and short-time Fourier transform （STFT） are widely used.Because they are expressed as a fixed time-frequency domain,they have the disadvantage that the time information about the signal is unknown.In order to overcome these limitations,by using the wavelet transform that provides a variety of time-frequency resolution,multi-resolution analysis can be analysed and a varying noise depending on the time characteristics can be removed more efficiently.Therefore,in this paper,a denoising method of underwater vehicle using discrete wavelet transform （DWT） is proposed.