In this paper, the problem of robust tracking for robot manipulator is considered. On the basis of slidingmodecontrol theory, a class of VSC controllers for robust tracking of robotmanipulators is proposed under decentralized approaches. It is shown theoretically that for system with matched uncertainties, the tracking error is guaranteed to decrease asymptotically to zero and the system dynamics during the sliding phase can easily be shaped up using any conventional pole placement method.
system and treat each joint of the manipulator as a simple linear servomechanism as in most of industrial robots, whereby the simple controller like Independent Joint Control (IJC), proportional plus derivative (PD), or proportional plus integral plus derivative (PID) controllers are adopted. In these methods, the nonlinear, coupled and time-varying dynamics of the mechanical linkage of the robot manipulator have been excluded and completely ignored, or assumed as disturbances. Manipulators that have been controlled by this method usually move at slow speeds with unnecessary vibrations. In general, the method is only suitable for relatively slow manipulation and limited precision tasks . However, when the manipulator joints are moving simultaneously and at high speed, the nonlinear coupling effects and the interaction forces between the manipulator links may affect the performance of the overall system and increase the tracking error. The disturbances and uncertainties such as variable payload in a task cycle may also reduce the tracking quality of the robot manipulator system .
Line follower robot is mobile robot and has been widely used in different area. The usages of mobile robot are to transport material form one place to another place. Other than that, mobile robot also has been used in military as bomb defusing. However, the development of line follower robot has faced some difficulties mostly to obtain stable and precise navigation. When the speed of line follower is increased, the robot would not be able to navigate effectively or follow the line precisely. This is due to the slow response from the sensors, unstable wheels and other disturbances. These problems would be affecting to the performances of the robot.
The demand of Flexible Base Mobile Manipulator (FBMM) has risen in recent years and the applications are many and varied. This research proposed new Combined SlidingMode Impedance Control (SMIC) for FBMM using singular perturbation method. FBMM applications include robotic manipulator mounted on the mobile vehicle in space, under water or on the land. These applications include position/force control requirements so on welding, cleaning, machine tooling, construction, finishing and inspection. Meanwhile, assumption of rigid base is unreal for all kind of FBMM. Impact value of mobile manipulators depends to both base motion and links masses which cause greater vibration on the flexible base at the contact point.
The application of adaptive neural networks to robot manipulator is presented in Perez et al. (2012) which explain recurrent neural networks and Lyapunov function methodology. An adaptive type-2 FLC for flexible-joint manipulators with structured and unstructured dynamical uncertainties have introduced in (Chaoui et al., 2012). In Abdel et al. (2011), the author has proposed fuzzy partition to the state variables based on the Lyapunov synthesis. Authors in Zeinali and Notash (2010) and Ho et al. (2009) have presented a methodology that enables the designer to systematically derive the rule base of the control. In Kohrt et al. (2013), authors have discussed on-line robust control for robot manipulator. This paper presents a new adaptive SMC for 2DOF robot manipulator; an adaptive tracking controller with a PID sliding surface. The adaptive SMC algorithm can estimate the value of switching gain constant (K w ) and boundary
The maximum error of six legs for the proposed controller is about 1mm, in other words, the position tracking results of our method are relatively crude but still sufficient in the practical applications. However, although the classical FSMC controller can satisfy the trajectory tracking performance of the 6-DOF parallel robot, the velocity control results (as in Fig. 11(b)) cannot meet the requirement of robotics for medical purpose, since the chattering is distinct especially in high speed situations. The reason why velocity tracking performance is so concerned in this rehabilitation practice is conducted as follows. Lower limb rehabilitation robots have to be manipulated within a wide range of speeds. In practical implementations, velocity chattering is highly undesirable because it may impact the plant dynamics and thus result in unforeseen instabilities, which is especially destructive in the training process. However, among researches on fuzzy slidingmodecontrol, only a few considered the chattering characteristics of the velocity tracking control. In papers (36-38), the systems all realized trajectory tracking in simulation or practical environment. A cascade-control algorithm based on slidingmode was proposed in Ref. 27 to realize the trajectory tracking control of a parallel robot. However, the system lacked direct measurements of the velocity signal, and the velocity observer was designed using the position error, which may introduce severe noises.
A robot is an electro-mechanical device guided by computer programs and applications, and is a combination of mechanical engineering, electrical engineering and computer science. A robot is generally constructed and designed based on human and biological nature. The purpose of creating robots is to replace human work that is tiresome, repetitive, or dangerous. This could be military and police work, such as the manipulation of explosive devices or the access to places that are difficult to reach by humans, such as space (Moosavian & Papadopoulos, 2007) or the bottom of the sea (Salvador et al., 2013), due to extreme environments which humans are unable to survive. Due to the limited working space, the first robotic surgery was successfully performed by two main robots called McSleepy and DaVinci, which allowed the surgeon to work with delicate and precise hand movements of fingers that would be impossible to be done by humans alone (Science Daily, 2010).
In this paper, a simulink library is presented for modelling robot manipulator functionalities and how the trajectory will follow the end effector manipulator input and what is the difference between desired and the actual trajectories. This model based approach supports with only revolute joints and excludes the Prismatic joints. In future, the other variants like mobile robots, spherical and parallel robots can be developed. The library currently does not include blocks to perform robot dynamics. There are other variants of stationary robots, for example, cylindrical robot, spherical robot and parallel robot; and mobile robots, for example, wheel robot and legged robot, which Model Rob Library currently does not support. The main objective of this paper is to show that the model-based development approach can be successfully applied to the development of robot software and to motivate development of exhaustive library to cover all variants of robots.
tion mode transformation of a mobile robot with wheel-arms. The proposed method aims at transformation from a four-wheeled mode for high speed mobility to an inverted pendulum mode, which has advantages of high viewing position and small turning radius. Since the initial state of the system is far away from the target equilibrium point of the wheeled inverted pendulum system, we use a nonlinear controller based on slidingmodecontrol. In contrast that the previous transformation methods cannot control the robot velocity until the robot body is lifted up, the proposed method can take into account the robot velocity from the beginning of the transformation, which enables to complete the transformation in a smaller space. To analyze the asymptotic stability of the control system on the sliding surface, we derive an invariant set in which the system state converges to the origin without going out. Furthermore, the effectiveness of the proposed method is demonstrated in both simulations and real robot experiments.
Abstract—A simple PS adaptive integralslidingmode controller is designed for the pitch channel linear model of supersonic missile firstly. In order to improve the performance of the proposed method, two improvements also proposed. Finally, a hybrid PISS adaptive control is formed which contains proportion control, integration control, the sign function adn soft function. Also nurmerical simulations are done to the testify the above theory. And it shows that both the proportion control and sign function control methods are unable to achieve a satisfactory performance for supersonic missile system. And the integration of soft function , integralcontrol item and proportion control can solve the chattering problem and static error problem. At last, simualtion figures shows that the PISS mehtod also has a strong robustness, which is testified by increasing or decreasing air-coefficients of the missile system .
According to the mechanical structure and operation principle of differential-drive two-wheeled robot, and aiming at the nonlinear systems with uncertainties variable structure, a trajectory tracking model based on slidingmodecontrol (SMC) was designed by utilizing state vector to establish the model of system and controller. The simulating results show that robot can track line, circle and S shape trajectories well, which gave reasonable dynamic responses, adjustment performance, as well as perfect disturbance rejection. The system can eliminate errors according to the deviation from sliding surface by switching the structure of controller and is robust to external disturbance.
Slidingmodecontrol deals with the problem of model uncertainties as these uncertainties can have strong adverse effects on nonlinear control systems. A major approach to deal with the model uncertainly is adaptive control and another approaches which can be used to solve the control problems includes the slidingmode techniques. These techniques are generating greater interest nowadays. Discrepancies may occur between the actual plant and the mathematical model established for the controller design. Various factors may be responsible for this mismatch. The engineer’s role is to ensure required performance levels for the system instead of such mismatches. A set of robust control methods have been developed to eliminate any error. One such method is slidingmodecontrol methodology(SMC). This is a specific type of variable structure control system (VSCS). SMC has been used for several systems including nonlinear system, multi-input multi- output(MIMO) systems, discrete-time models, large-scale and infinite-dimension systems, and stochastic systems. SMC is completely insensitive to parametric imprecisions and external disturbances during slidingmode. VSC uses a high-speed switching control law to accomplish two objectives. Firstly, the nonlinear plant’s state trajectory is taken onto a specified and user-chosen surface in the state space which is called the sliding or switching surface. This is called as the switching surface because a control path has a unique gain if the state trajectory of the plant is “above” the surface and a different gain if the trajectory falls “below” the surface. Secondly, it keeps the plant’s state trajectory on this surface for all consequent times. During this process, the control system’s structure changes from one to another and thus given the name variable structure control(VSC). The control is also named as the slidingmodecontrol to accentuate the importance of the slidingmode. Slidingmode controller can stabilize the trajectory of a system. Control structures are designed so as to ensure that trajectories will always move towards a switching condition. Therefore, the ultimate trajectory will not exist completely within one control structure. Instead, the ultimate trajectory will slide along the boundaries of the control structures. The motion of the system as it slides along these boundaries is termed as a slidingmode and the geometrical locus consisting of the boundaries is called the sliding (hyper) surface. The slidingmode phases are shown in figure 2
Electro-hydraulic servo (EHS) system has emerged a great interest in various engineering applications due to its advantages as an actuator in providing high forces with compact design . The sophisticated design of EHS system with the versatility of electronic and hydraulic components offers a great performance and improvement for wide range of applications such as aircrafts , manufacturing machines , fatigue testing  and automotive application . It is established that the EHS system can be more well-known and crucial nowadays.
Electro-hydraulic actuator (EHA) systems have grown to be one of the most popular actuators in modern applications for several decades. EHA systems can be found easily in production assembly lines, robotics, automotive, aircraft, submarine operations, mining processes, etc. This is due to the fact that EHA systems have fast and smooth response characteristics and high power density. EHA systems also have excellent capability in positioning that gives a significant influence to the above applications especially in position tracking control issues. However, as introduced in Yao et al. (2000), EHA systems exhibit highly nonlinear behaviours, such as nonlinear servo valve flow-pressure characteristics, variations in control volumes, dead-band, stiffness, internal leakage, and associated friction. Apart from the nonlinear natures, parametric uncertainties, uncertain nonlinearities and disturbances also become large extent of EHA systems. Hence, consideration on these issues to obtain more accurate model in the modelling of EHA systems is essential.
In addition, parameter estimation has been identified as one of the ways, through which the accuracy of MSMC can be improved. Hybrid optimization is quite well-known in many application . Several studies have proposed the combination of GSA and PSO it was through such studies, it was learnt that the combination of PSO and GSA is capable of providing improved results for general mathematical functions . However, both have looked into the generic algorithms and it has yet to be specifically applied to estimate the parameters of MSMC controller for mismatched disturbance system such as an electro-hydraulic actuator such as the case in the present study. More importantly, no studies, at least to the knowledge of the researcher, have considered looking into parameters estimation for MSMC to enhance its accuracy and performance.
The study of fault tolerant control (FTC) has received much attention in the last decade. Many different schemes have been proposed, ranging from active to passive control methods , with applications running the gamut from large scale petrochemical plants to automotive and aerospace systems . The work in , , ,  provides an excellent literature review on the different schemes used for FTC including different applications; however, research into FTC has been significantly driven by problems encountered in the safety critical aerospace industry. This is due to the practical requirement for increasing safety as well as lowering operational costs. Many different FTC methods, specific to aircraft applications, have been proposed including linear approaches (e.g. H ∞ , LQG , model-following , multiple model , model predictive control ), and nonlinear approaches (e.g. nonlinear dynamic inversion , backstepping , neural networks , slidingmode ). Some of these methods have attracted the attention of industry and have been further tested and evaluated in order to assess their potential for future applications and implementations on aircraft (see for example the European study on state-of-the-art FTC by the GARTEUR AG-16 group  and the recent ADDSAFE project ). However many of these proposed FTC schemes are based on linear plant representations and are therefore only valid in the vicinity of the designed trim point. Therefore, one of the main challenges for practical implementation, especially for aircraft, is to ensure good performance for a wide range of operating conditions. Some of the linear based designs can be extended to handle variations in operating conditions (see for example, gain scheduling and linear parameter varying (LPV) schemes , ), but direct nonlinear methods such as nonlinear dynamic inversion (NDI) and backstepping provide equally viable alternatives – with many benefits compared to the extended linear cases. One obvious benefit is the direct exploitation of the well known aircraft equations of motion, which provide good and consistent performance throughout the flight envelope.
In order to make the spherical underwater robot better finish the task of underwater operation, the good control system and control method are essential. Researchers have proposed a variety of motion control methods, and the control algorithms of underwater which have been applied: PID control, improved PID control, fuzzy control, adaptive control, slidingmodecontrol, neural network control, robust control, and some combination of these control algorithms. Slidingmodecontrol (SMC), which is robust to model uncertainty and to parameter variations, and it has good disturbance rejection features. There have been a wide variety of applications of it [4,5,6,7,8,9,10,11] . However, it inherits a discontinuous control action and hence chattering phenomena will take place when the system operates near the sliding surface. Sometimes this discontinuous control action can even cause the system performance to be unstable. Fuzzy Control (FC) has supplanted conventional technologies in many applications. One major property of fuzzy logic is its ability to express the amount of ambiguity in human thinking. Therefore, when the mathematical model of the process does not exist, or exists but with uncertainties, FC is an alternative way to deal with the unknown process. However, the huge number of fuzzy rules for high-order systems makes the analysis complex [12,13,14,15] . The system used in this paper is a combination of fuzzy control and the slidingmodecontrol.
1. Soon, C. C., Ghazali, R., Jaafar, H. I. and Hussein, S. Y. S., 2015. "Optimizing PID Controller for an Electro-hydraulic Servo System via Gradient Descent Technique," Proceedings of Mechanical Engineering Research Day 2015 (MERD'15), 31 Mac, Melaka, Malaysia. (Indexed by Thomson Reuters, Web of Science)