Zool Hilmi Ismail

Redundancy resolution for underwater vehicle-manipulator systems with congruent gravity and buoyancy loading optimization

In this paper, a new redundancy resolution scheme is proposed for an underwater vehicle manipulator system (UVMS). Using the proposed resolution technique, the systems redundancy is exploited so as to minimize gravity and buoyancy loading of the UVMS which is composed of subsystems with different dynamic responses. The generalized velocity components (GVC) approach is considered in order to obtain a congruent gravitational expression which consists not only of vehicle pose but also the onboard manipulator configuration. During end-effector motion, the overall systems control effort is reduced if gravity and buoyancy loading of both subsystems are small values. A new performance index is applied using the local redundancy resolution. Results from simulations are presented to demonstrate the benefits of the proposed performance index.

Second Order Sliding Mode Control Scheme for an Autonomous Underwater Vehicle with Dynamic Region Concept

The main goal in developing closed loop control system for an Autonomous Underwater Vehicle (AUV) is to make a robust vehicle from natural and exogenous perturbations such as wind, wave, and ocean currents. However a well-known robust control, for instance, Sliding Mode Controller (SMC), gives a chattering effect and it influences the stability of an AUV. Furthermore, some researchers combined other controls to get better result but it tends to present long computational time and causes large energy consumption. Thus, this paper proposed a Super Twisting Sliding Mode Controller (STSMC) with dynamic region concept for an AUV. STSMC or a second order SMC is adopted as a robust controller which is free from chattering effect. Meanwhile, the implementation of dynamic region is useful to reduce the energy usage. As a result, the proposed controller obtains global asymptotic stability which is validated by using Lyapunov-like function. Moreover, some simulations present the efficiency of proposed controller. In conclusion, STSMC with region based control is effective to be applied for the robust tracking of an AUV. It contributes to give a fast response when handling the perturbations, short computational time, and low energy demand.

Position Control of Pneumatic Actuator Using Self-Regulation Nonlinear PID

The enhancement of nonlinear PID (N-PID) controller for a pneumatic positioning system is proposed to improve the performance of this controller. This is executed by utilizing the characteristic of rate variation of the nonlinear gain that is readily available in N-PID controller. The proposed equation, namely, self-regulation nonlinear function (SNF), is used to reprocess the error signal with the purpose of generating the value of the rate variation, continuously. With the addition of this function, a new self-regulation nonlinear PID (SN-PID) controller is proposed. The proposed controller is then implemented to a variably loaded pneumatic actuator. Simulation and experimental tests are conducted with different inputs, namely, step, multistep, and random waveforms, to evaluate the performance of the proposed technique. The results obtained have been proven as a novel initiative at examining and identifying the characteristic based on a new proposal controller resulting from N-PID controller. The transient response is improved by a factor of 2.2 times greater than previous N-PID technique. Moreover, the performance of pneumatic positioning system is remarkably good under various loads.

A region boundary-based geometric formation control scheme for multiple Autonomous Underwater Vehicles

In this paper, a simple control approach based on a region boundary technique for geometric formation of multiple Autonomous Underwater Vehicles (AUVs) is presented. The control objective is to keep each underwater vehicle at each corner of a desired geometric shape, i.e. an equilateral triangle or a square. An edge-based segmentation approach is utilized rather than specifying the minimum distance between members to ensure that each vehicle is placed exactly at the desired position in their formation. This allows each vehicle that has its own function to carry out an effective individual task, thus improving the formations performance. The model of the ODIN vehicle is used as an example to demonstrate the proposed controller. Simulation results show the effectiveness of the controllers.

An adaptive region boundary-based control scheme for an autonomous underwater vehicle

A new control concept is proposed for an autonomous underwater vehicle (AUV) where the desired target is defined as a boundary rather than a point or a region. The inverse Jacobian is utilized in the adaptive control law for compensation of the persistent effects i.e.: the restoring forces. The unit quaternion representation is used for the AUVs attitude representation. The stability analysis is carried out using a Lyapunov-like function. Simulation results are presented to access the effectiveness of the proposed control scheme.

Fault-Tolerant Region-Based Control of an Underwater Vehicle with Kinematically Redundant Thrusters

This paper presents a new control approach for an underwater vehicle with a kinematically redundant thruster system. This control scheme is derived based on a fault-tolerant decomposition for thruster force allocation and a region control scheme for the tracking objective. Given a redundant thruster system, that is, six or more pairs of thrusters are used, the proposed redundancy resolution and region control scheme determine the number of thruster faults, as well as providing the reference thruster forces in order to keep the underwater vehicle within the desired region. The stability of the presented control law is proven in the sense of a Lyapunov function. Numerical simulations are performed with an omnidirectional underwater vehicle and the results of the proposed scheme illustrate the effectiveness in terms of optimizing the thruster forces.

Application of optimization technique for PID controller tuning in position tracking of pneumatic actuator system

In this paper, two optimization techniques of Particle Swarm Optimization (PSO) and Firefly Algorithm (FA) is used to obtain the optimal PID control parameters. To represent the model of the system, system identification with ARX model structure is developed. The results are determined by analysis the step response characteristic of the system. It was observed that the performances of PID controller with PSO optimized parameters perform well in position tracking of the pneumatic actuator system.

Power Harvesting in Wireless Sensor Networks and Its Adaptation With Maximum Power Point Tracking: Current Technology and Future Directions

Wireless sensor networks (WSNs) is one of the most effective tools in collecting data autonomously going as recently as 5–10 years ago. A low deployment and maintenance cost WSN is highly recognized as one of the more advanced Internet of Things networks that can be deployed for a series of purposes namely environmental and industrial monitoring due to the majority of such systems run on expendable power source that offers WSN with a limited service lifetime. The aim of this paper is to review existing renewable energy and prospective approaches in energy harvesting strategy as a means of having a sustainable and low maintenance operation of WSN. Additionally, recent maximum power point tracking (MPPT) of solar energy harvesting is thoroughly discussed in a new perspective of the WSN framework. Semi-pilot cell fractional open-circuit voltage (SPC-FOCV) MPPT is a fairly new concept in WSN application that features less complicated configuration with reduced hardware requirements and lower cost. Recent research findings are evaluated throughout this paper leading to the SPC-FOCV MPPT materialization. A holistic discussion is made encompassing the advantages and disadvantages of the concept, its performance compared to conventional MPPT approaches and the future insight of the technology in WSN.

Nonlinear H ∞ optimal control scheme for an underwater vehicle with regional function formulation

A conventional region control technique cannot meet the demands for an accurate tracking performance in view of its inability to accommodate highly nonlinear system dynamics, imprecise hydrodynamic coefficients, and external disturbances. In this paper, a robust technique is presented for an Autonomous Underwater Vehicle (AUV) with region tracking function. Within this control scheme, nonlinear and region based control schemes are used. A Lyapunov-like function is presented for stability analysis of the proposed control law. Numerical simulations are presented to demonstrate the performance of the proposed tracking control of the AUV. It is shown that the proposed control law is robust against parameter uncertainties, external disturbances, and nonlinearities and it leads to uniform ultimate boundedness of the region tracking error.

A sub-region boundary-based control scheme with a least-squares estimation algorithm for an underwater robotic system

A new control concept is proposed for an underwater vehicle-manipulator system (UVMS) where the desired target is defined as a region boundary rather than a point or a region. For a mapping of the uncertain persistent effects i.e.: the restoring forces, a least-squares estimation algorithm along with the inverse Jacobian matrix is utilized in the adaptive control law. The unit quaternion representation is used for the attitude representation. The stability analysis is carried out using a Lyapunov-like function. Simulation results are presented to assess the effectiveness of the proposed control scheme.