Three-Dimensional Path Tracking of Over-Actuated AUVs Based on MPC and Variable Universe S-Plane Algorithms

The interaction force control problem for the object manipulated by the dual-arm manipulator with the unknown environment is addressed in this paper. An adaptive dual-loop impedance control scheme is designed to meet the three control targets, including the trajectory tracking control of the object, the internal force control of the object with the two arms, and the interaction force control of the object with the unknown environment. Firstly, an adaptive variable impedance control method is proposed in the outer loop to copy with the unknown stiffness and position of the environment. Secondly, an impedance control scheme based on the internal force is designed in the inner loop to plan the internal force and the modified position supplied with the outer-loop control. Thirdly, to realize the reference trajectory supplied with the inner-loop control, the virtual decomposition control (VDC) method is incorporated, which is a recursive adaptive control progress, so that the unknown dynamics of the manipulators is acceptable and the computation complexity is also very low to satisfy the real-time control requirement. The stability verifications of the inner-loop impedance control and the VDC method are given based on the Lyapunov method, and the stability analysis of the outer-loop impedance control is obtained using the Routh criterion. Finally, a plane dual-arm robotic manipulator with three degrees of freedom is used to verify the effectiveness of the proposed control scheme.

In this paper, a cascaded nonlinear control design for the position of a hydraulic servo cylinder is presented that is based on a control-oriented mathematical model of the test rig. The difference pressure is controlled in the inner loop, whereas the position control is addressed in the outer control loop. Additionally, the outer position control loop is extended by a combination of feedforward friction compensation and an observer-based disturbance compensation to improve the position tracking behaviour. Thereby, the benefits of both measures can be exploited: fast reaction and robustness w.r.t. remaining parameter uncertainties and inaccuracies in the friction model. As the system states are measurable, a reduced-order disturbance observer is designed. The efficiency of the overall control structure and the impact of the individual control actions are pointed out by experimental results obtained at a test rig at the Chair of Mechatronics, University of Rostock.

The phase-locked loop (PLL)-based grid-following inverters have been widely used as the interface between renewable energy resources (e.g., wind and solar power) and the utility grid. In addition to the basic PLL and inner current control loop that are responsible for tracking the phase angle of the point of common coupling (PCC) voltage and regulating the current injection according to the estimated phase angle, respectively, these grid-following inverters are commonly also equipped with outer power and voltage control loops. Some examples are outer active power/dc-link voltage control loops and outer reactive power/PCC voltage control loops, which provide the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$dq$ </tex-math></inline-formula> -axis current references for the inner current control loop. However, the existing literature generally focuses on specific outer control modes within a specific small-signal modeling framework, e.g., state-space or admittance modeling framework. In addition, different research groups usually repeatedly derive these small-signal models without a systematic modeling and analysis procedure. Furthermore, the systematic and comprehensive comparative modal and admittance analysis of these outer control modes is still missing in the literature. To avoid reinventing the wheel, provide the small-signal stability analysis community with handy both state-space and admittance models, and investigate the effects of various outer control loops on the small-signal models, this article presents a comprehensive and systematic small-signal modeling, analysis, and comparison framework of the PLL-based grid-following inverters, where the state-space and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$dq$ </tex-math></inline-formula> -domain admittance models of eleven control modes are derived step by step in a completely followable style. All of these derived small-signal models are verified by the time-domain step responses and frequency-domain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$dq$ </tex-math></inline-formula> -domain admittance measurement. The insights into the effects of these outer control modes on the poles and residues of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$dq$ </tex-math></inline-formula> -domain admittance model are also explored, which help to understand how these outer control modes contribute to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$dq$ </tex-math></inline-formula> -domain admittance shaping.

To solve the trajectory tracking problem of underwater vehicles in the presence of unknown dynamics and external disturbances, a double-loop adaptive integral sliding mode controller that yields chattering-free performance is proposed in this paper. The designed double-loop controller consists of an outer-loop position controller (the kinematic controller) and an inner-loop velocity controller (the dynamic controller). The outer-loop controller is designed based on the desired position and current position and it serves as the virtual control input to achieve accurate position tracking. A saturation function is adopted to replace the conventional signum function to overcome the chattering problem of the outer-loop sliding mode. And then, the outer-loop controller is considered as the reference velocity for the inner loop, and the inner-loop controller (the real control input) is developed to make the actual velocity of the vehicle to precisely track the reference velocity. A continuous adaptive term is designed instead of the discontinuous switching term in the conventional sliding mode to estimate and compensate the unknown dynamics and external disturbances and to eliminate the chattering effects of the inner-loop sliding mode. The global asymptotical stability of the double-loop tracking system is analytically proven using Lyapunov stability theory and Barbalat's lemma. Numerical simulation performed on the dynamic model of ODIN AUV demonstrates the effectiveness of the proposed approach.

A control system based on the principle of forced dynamics control for an electric drive with a permanent magnet synchronous motor and a flexible coupling is presented and verified by simulations. The controller is of the cascade structure, comprising an inner speed control loop and an outer position control loop. The inner forced dynamics speed control loop respects the principles of vector control and requires an estimate of the load torque, which is estimated in an observer. The outer position control loop based on the same principle is designed to control the rotor angle or load mass angle in the presence of a vibration mode due to the flexible coupling and with an external load torque. The derived control law requires estimates of the load torque and its derivatives, which are estimated in the load torque observer. The simulations presented indicate that the control system operates according to theory and therefore further investigations including experimental implementation are recommended.

This paper presents quaternion based twisting and backstepping controller for quadrotor. The quaternion model is free from singularity problem unlike the Newton Eulers model. There are two types of controller is designed, one for inner loop control and second is the outer loop control. In the proposed work inner loop controller is backstepping and outer loop control is twisting control. Inner loop control is also termed as attitude control. In attitude control reference velocity is generated using reference quaternion model. Both inner loop and outer loop controller are robust enough to handel disturbances. Stability is guaranteed using Lyapunov method. Simulation results are presented for different generated paths to show the advantage of the proposed method.

This paper proposes a novel diving plane control scheme for autonomous underwater vehicle (AUV) based on tracking differentiator (TD) and cascade control (CC). The outer loop controller and inner loop controller adopt PI and P, respectively. Firstly, the mathematical model of AUV is established. The model consists of two parts: one is the depth model, and the other is the pitch model. Then, both controllers are designed by using CC with the tracking differentiator. The TD can filter the white noise of input signals and make the noise have little influence on control performance. Simulation results demonstrate the effectiveness of the proposed method.

An existing sampled-data control algorithm for double integrator systems with pre-determined inter-sample behavior is generalized to incorporate disturbance rejection in addition to command tracking. The proposed control system comprises an inner velocity control loop and an outer position control loop. A discrete-time compensator is used to regulate velocity and reject step disturbance in acceleration due to forces or moments on the system. The outer loop produces a pre-determined, piecewise constant (bang-bang) signal proportional to the position tracking error that defines the desired inter-sample position and velocity behavior. Simulation results of the disturbance rejection performance are presented.

This paper presents a technique to cope with undesirable frictional effects in positioning control of a pneumatic actuator. This technique is based on an observer for estimating the dynamically varying friction force on-line. The observer is derived from an available nonlinear observer for Coulomb friction by modifying it to fit the pneumatic actuator and to enhance its estimation ability. Our pneumatic servo system for positioning consists of an inner pressure control loop, an outer position control loop, the friction observer, and a velocity observer. In this system, the friction force is compensated by adjusting a desired pressure value sent from the outer loop to the inner loop according to the friction observer output. Experimental comparisons with a conventional control system using friction compensation by means of accelerometer information feedback were carried out and show that our system works with almost the same high positioning accuracy as the conventional system, despite having neither an accelerometer nor a velocity sensor, and is more advantageous from the perspective of cost performance.

&lt;span&gt;This paper is presented for designing a new controller using the predictive model current and speed control method for the asynchronous motor. This control method is based on traditional predictive controller development to have a cascade structure similar to the rotor flux control (field-oriented control) and direct torque control (DTC). Therefore, this control method will have two control loops. Both inner and outer loop controllers use predictive power. The outer ring is speed control, while the internal circle is stator current control. The inner loop is based on the finite control set – model predictive control (FCS-MPC), while the outer ring to take full advantage of the high dynamic response of the inner circle uses the deadbeat MPC. MATLAB simulation results show that this control method has performance equivalent to traditional controllers while minimizing overshoot and having fast, on-demand response times.&lt;/span&gt;

In recent years, precious observations by autonomous underwater vehicle (AUV) have been performed. Tracking and navigation of AUV are important for precious observations. In Japan agency for Marine-earth Science and Technology (JAMSTEC) the observations with AUV ldquoURASHIMArdquo have been implemented in deep ocean area. AUV URASHIMA is navigated by an inertial navigation system (INS) mainly. The absolute position of AUV is tracked on the support vessel with super short base-line (SSBL) method of acoustic positioning. And sometime the own position in AUV is updated by the SSBL estimation result to correct the drift error of INS. However the SSBL is not so accurate. So the position correction includes the SSBL error and the position correction is performed drastically. In this paper, a method for accurate tracking of AUV and rapid correction of the INS status is proposed. The tracking is mainly achieved by SSBL on the support vessel. Additionally the INS data is transmitted from AUV including the acoustic positioning signal. The INS output of relative position to past own position is very accurate within short time. The INS data is used for tracking. Furthermore the position result estimated on the vessel is transmitted to AUV with next interrogation signal. And the own position in AUV is rapidly updated with accurate estimation. Some digital data including INS data is modulated with phase shift keying (PSK) method and direct sequence spread spectrum (DSSS) technique for transmission with acoustic positioning signal. The proposed method was considered by simulation. And good results were obtained.

As a single controllable unit, microgrid can be grid-connected with utility grid and detached from grid to become a controllable autonomous system. When microgrid is switching between grid-connected mode and islanding mode, it will cause fluctuation of voltage, current and frequency, which will have a certain impact on the load. The stable control in both modes is the basic condition to ensure the reliable operation of microgrid. In this paper, control strategy of grid-connected and islanding mode switching based on the master-slave structure of microgrid system is mainly researched. The proposed method of PQ outer loop controller, V/f outer loop controller and current inner loop controller of the master inverter of microgrid is given. Based on the analysis of the structure of the controller, a mathematic model of the master inverter of the microgrid is established, and a current inner loop controller based on the LADRC (Linear Active Disturbance Rejection Control) technique is designed. The presented smooth switching control strategy makes the outer loop controller running in parallel, and the inner loop controller share the improved current inner loop controller. LADRC control structure has strong anti-interference ability, it can effectively inhibit the fluctuations of various parameters, has a good inhibitory effect on the uncertainty of the power grid. The design method is simple and feasible. The simulation results show that the switching range of voltage, current and frequency is small, and the switching process time is less than 20ms, which can achieve stable and smooth switching between microgrid and utility grid.

Fuel cell is an attractive alternative to generate clean electricity for many industrial applications. This paper discusses model predictive control (MPC) of a fuel cell-based power unit (FC-PU) for vehicular applications. The MPC improves the transient response of the FC-PU. In this FC-PU, a unidirectional converter controls the current of a proton exchange membrane (PEM) fuel cell, and a bidirectional converter controls the output DC link voltage by regulating the battery current. The proposed MPC structure in the continuous control set (CCS) scheme has a fixed switching frequency and employs two different sampling frequencies to provide MPC for both inner and outer control loops. This controller provides a fast response to the changes in the reference values of the control variables or system transients such as load transients. It is also robust against parameter mismatch. Simulation results validate the proposed controller via several simulation case studies.

Forced dynamics control principles are exploited to develop control algorithms for electric drive with PMSM and flexible couplings. The controller is of the cascade structure, comprising an inner speed control loop, which respects the principles of vector control and requires a load torque estimate and an outer position control loop, which is designed to control the PMSM rotor or load angle in the presence of the vibrations due to flexible coupling including an external load torques. Computation of PMSM stator voltage is based on novel algorithm exploiting forced dynamics control. Derived control laws require the estimates of the load torque and its derivatives estimated in the set of observers. Control algorithm is verified by simulations and preliminary experiments indicating good agreements with theoretical predictions, therefore further experimental verification of the designed control algorithm is recommended.

Optimal power extraction control schemes for five-phase PMSG based wind generation systems