Abstracts:In order to meet the rigorous requirement for transient and static performance of automobile electronic throttle control systems, an adaptive finite time servo control (AFTSC) strategy is investigated by integrating adaptive backstepping recursive technique into the framework of finite-time stability theory. The required transient performance of the throttle opening trajectory tracking is guaranteed theoretically by the finite convergence time and the convergence rate related to the adjustable control parameters. The static performance is enhanced by introducing the tracking error integral into the system state variables. The robustness of the satisfactory transient and static performance is improved by the adaptive update law in the light of system parameter uncertainties due to production deviations, different working conditions and aging. Meanwhile, the advantage of the proposed AFTSC strategy is validated by demonstrating the comparison results with the existing strategies both in the critical operating cases under Matlab/Simulink simulation environment and in the actual operating cases on the dSPACE rapid-control-prototype (RCP) test platform for a real electronic throttle system.

Abstracts:Maglev (magnetic levitation) system has been introduced as one of innovative technologies that transportation is able to move without contacting on the ground so that it has immensely beneficial in eliminating friction and generating high speed. Having some advantages of generating less friction and dusts in maglev technology, we design a high accuracy maglev tray system to carry organic light-emitting diode (OLED) display. To carry OLED display in a stable condition, it is necessary to control precisely the levitation state. In our paper, a multi-degree of freedom model for a high precision maglev tray system analyzed to consider the stability and robustness of levitation performance. This model is then used to design a cascade control strategy and a combined optimal state-feedback controller–observer compensator for the heave, roll and pitch motion of maglev tray system. The proposed controllers demonstrate the excellent levitation performance under comparative simulations such as a large load disturbance and sensor installation error.

Abstracts:This paper describes an active vibration control system combining a piezoelectric electrode configured with a novel switching control system to achieve multimodal vibration suppression in smart flexible structures embedded with only a single piezoelectric actuator. The fact that high-frequency vibrations attenuate more rapidly than do low frequency vibrations motivated the development of a novel scheme in which the resonant excitation of coupled bending and lateral vibrations is applied to a cantilever beam. Switching times are determined using time-frequency analysis of modal responses. A smoothing function was applied to alleviate the effects of high-frequency oscillations during the switching control transition in order to facilitate the suppression of bending mode vibrations. Algorithms for proportional derivative (PD) control and positive position feedback (PPF) control can be tailored specifically for the target vibration modes and implemented in a variety of switching control schemes. The vibration responses induced by various switching control schemes was analyzed in order to derive appropriate control parameters for the development of an efficient switching control system aimed at suppressing multimodal vibrations. Experiment results demonstrate the effectiveness of the proposed piezoelectric electrode configuration in suppressing lateral mode vibrations. The proposed switching control system also proved highly satisfactory in suppressing vibrations in a system subject to simultaneous bending mode excitation.

Abstracts:One of the issue of significant interest for robotics is the fault detection, specifically when we have application in risky circumstances. Robotic systems required a capacity to efficiently identify and endure some defects so that they can keep achieving the required tasks while avoiding instantaneous repairing process. Consequently, we aim in this work to propose a systematic approach for state estimation and fault detection technique to enhance the operation of humanoid robots (HR) systems using an extended Kalman filter (EKF)-based multiscale optimized exponentially weighted moving average chart (MS-OEWMA). The objectives of this work are sixfold: (1) apply EKF technique to estimate the state variables in HR systems. The EKF is among the most popular nonlinear state estimation methods; (2) use dynamical multiscale representation for obtaining accurate settled characteristics; (3) propose a new optimized EWMA (OEWMA) based on the best selection of both smoothing parameter (λ) and control width L; (4) combine the advantages of state estimation technique with MS-OEWMA chart to improve the monitoring of HR systems; (5) investigate the effect of fault types (change in variance and mean in shift) and fault sizes on the monitoring performances; (6) validate the developed technique using two robot models: inverted pendulum and five-bar linkage. The detection results are evaluated using three fault detection metrics: missed detection rate (MDR), false alarm rate (FAR) and out-of-control average run length (ARL 1).

Abstracts:Inspired by nature, many types of artificial muscles or actuators have been developed for mechatronic systems. Twisted and coiled polymer (TCP) muscles are some examples that are made from nylon or polyethylene. The muscles contract over 20% strokes under considerable load. There are limited studies available on the modeling and control of these muscles for practical use. In this paper, we show discrete-time modeling and control of the force of the muscles. Prediction error method (PEM) was used for parameter estimation of discrete-time state space models to find the order of the model. Then, proportional–integral (PI) controller was demonstrated as a classical controller to regulate the force of the muscles. To increase the speed of actuation, a Takagi–Sugeno–Kang (TSK) controller was employed as a fuzzy controller. Our experimental results demonstrate how the muscle can be controlled in practical settings and shows the superiority of TSK over the PI controller. We anticipate that the model and controllers will add new knowledge for the use of the twisted and coiled polymer muscle in mechatronic system.

Abstracts:In Natural Orifice Transluminal Endoscopic Surgery (NOTES), a surgical robot that can access the human colon or stomach via natural orifices should have sufficient flexibility to pass through tortuous paths and to be operated in a confined space. In addition, the robot should possess an acceptable stiffness level to hold payloads during the surgery. This paper presents a new design concept for variable stiffness manipulators using thermoplastic material Polyethylene Terephthalate (PET) and a flexible stainless steel sheath as a heating media. The stiffness phases of PET can be actively adjusted through temperature. Experiments at different conditions showed that the proposed design was at least as flexible as a typical commercial endoscope in compliant mode and at least 9 times stiffer than the endoscope in stiff mode. In addition, flexural modulus of the proposed manipulator with respect to temperature, current, and time was modeled and validated through both simulation and experiments. A tendon-driven flexible robotic arm integrated with a variable stiffness spine was also developed, and ex vivo tests on fresh porcine tissue were conducted. The manipulator in compliant mode can be easily controlled through the tendons, and it is able to hold its shape against considerably large loads in stiff mode. The results demonstrate not only the high potential of the design concept for the future medical application but also the first steps toward building a complete surgical robotic system with fully controlled variable stiffness.

Abstracts:An improved cerebellar model articulation controller (CMAC) based on the compound algorithms of credit assignment (CA) and optimized smoothness (OS) is proposed to improve the control performances of a three-axis inertially stabilized platform (ISP). On the basis of both advantages of CA and OS algorithms, the improved CMAC neural network controller can deal with the disadvantages of conventional CMAC in learning interference and output fluctuation. As a result, the main dynamic performances of the ISP control system are systematically promoted. To verify the method, the simulations and experiments are carried out respectively, in which the LuGre friction model is introduced to represent the main disturbances. The results show that the CA&OS-CMAC controller can efficiently restrain the nonlinear disturbances and obviously improve the ISP's pointing precision and output smoothness. Compared with the conventional CMAC controller, the root-mean-square (RMS) errors of tracking the angular position under the static base swinging and dynamic base leveling conditions are reduced by 17.17% and 30.55%, respectively.

Abstracts:The patients of paralysis with motion impairment problems require extensive rehabilitation programs to regain motor functions. The great labor intensity and limited therapeutic effect of traditional human-based manual treatment have recently boosted the development of robot-assisted rehabilitation therapy. In the present work, a neural-fuzzy adaptive controller (NFAC) based on radial basis function network (RBFN) is developed for a rehabilitation exoskeleton to provide human arm movement assistance. A comprehensive overview is presented to describe the mechanical structure and electrical real-time control system of the therapeutic robot, which provides seven actuated degrees of freedom (DOFs) and achieves natural ranges of upper extremity movement. For the purpose of supporting the disable patients to perform repetitive passive rehabilitation training, the RBFN-based NFAC algorithm is proposed to guarantee trajectory tracking accuracy with parametric uncertainties and environmental disturbances. The stability of the proposed control scheme is demonstrated through Lyapunov stability theory. Further experimental investigation, involving the position tracking experiment and the frequency response experiment, are conducted to compare the control performance of the proposed method to those of cascaded proportional-integral-derivative controller (CPID) and fuzzy sliding mode controller (FSMC). The comparison results indicate that the proposed RBFN-based NFAC algorithm is capable of obtaining lower position tracking error and better frequency response characteristic.

Abstracts:Friction modeling of hydraulic actuators is essential to system control and the prediction accuracies of friction models (e.g., Stribeck, LuGre) need to be improved when they were applied to hydraulically actuated systems. The test platform for hydraulic cylinders was constructed and the friction forces of plunger type hydraulic actuators were measured under different operating conditions. The dynamic behaviors of film thickness of seal/rod interface were investigated based on elastic hydrodynamic lubrication (EHL) method. The effects of acceleration of rod on friction force were examined using coherence function estimation technique. The Stribeck and LuGre model were modified by incorporating physically based hysteretic film dynamics and Bouc–Wen model into Stribeck function, respectively. It is shown that the Stribeck and LuGre model cannot preferably describe the friction force-velocity behavior, especially for the fluid lubrication regime. The modified Stribeck and LuGre model can simulate the hysteretic behavior of friction force-velocity loop more effectively than unmodified ones and the friction estimation accuracies of Stribeck and LuGre model were improved remarkably.

Abstracts:Equilibrium points exploration is crucial for successful nonprehensile manipulation of multi-link objects by cooperative arms which is promising for a class of future robotics applications. This paper presents the equilibrium area numerical analysis, with experimental verification, for nonprehensile manipulation of a three-rigid link object by two cooperative arms in a plane. Inspired by an assistive nursing robot project for manipulating a patient, the interaction between the object and the arms is performed in a way that one of the arms contacts two links of the object while the other arm contacts the object third link. It would be a useful step for the most complicated process of a patient manipulation. The purpose of the equilibrium area analysis is to obtain the equilibrium contact area, associated with different interaction forces, for statically holding the object at all its possible configurations. The dynamic model of the system is presented from which the static equations are deduced. Static equations are analyzed in the presence of friction forces and motion constraints leading to equilibrium contact lengths for a range of angles leading to equilibrium area for every object's configuration. Numerical simulation results for the equilibrium area analysis are presented. Experimental results, for validating the presented numerical results, are also introduced.