Development of 3D anti-Swing control for hydraulic knuckle boom crane

In this paper, 3D anti-swing control for a hydraulic loader crane is presented. The difference between hydraulic and electric cranes are discussed to show the challenges associated with hydraulic actuation. The hanging load dynamics and relevant kinematics of the crane are derived to model the system and create the 3D anti-swing controller. The anti-swing controller generates a set of tool point velocities which are added to the electro-hydraulic motion controller via feedforward. A dynamic simulation model of the crane is made, and the control system is evaluated in simulations with a path controller in actuator space. Simulation results show significant reduction in the load swing angles during motion using the proposed anti-swing controller in addition to pressure feedback. Experiments are carried out to verify the performance of the anti-swing controller. Results show that the implemented pressure feedback is crucial for reaching stability, and with it the control system yields good suppression of the swing angles in practice.publishedVersio

Development of Motion Control Systems for Hydraulically Actuated Cranes with Hanging Loads

Automation has been used in industrial processes for several decades to increase efficiency and safety. Tasks that are either dull, dangerous, or dirty can often be performed by machines in a reliable manner. This may provide a reduced risk to human life, and will typically give a lower economic cost. Industrial robots are a prime example of this, and have seen extensive use in the automotive industry and manufacturing plants. While these machines have been employed in a wide variety of industries, heavy duty lifting and handling equipment such as hydraulic cranes have typically been manually operated. This provides an opportunity to investigate and develop control systems to push lifting equipment towards the same level of automation found in the aforementioned industries. The use of winches and hanging loads on cranes give a set of challenges not typically found on robots, which requires careful consideration of both the safety aspect and precision of the pendulum-like motion. Another difference from industrial robots is the type of actuation systems used. While robots use electric motors, the cranes discussed in this thesis use hydraulic cylinders. As such, the dynamics of the machines and the control system designmay differ significantly. In addition, hydraulic cranes may experience significant deflection when lifting heavy loads, arising from both structural flexibility and the compressibility of the hydraulic fluid. The work presented in this thesis focuses on motion control of hydraulically actuated cranes. Motion control is an important topic when developing automation systems, as moving from one position to another is a common requirement for automated lifting operations. A novel path controller operating in actuator space is developed, which takes advantage of the load-independent flow control valves typically found on hydraulically actuated cranes. By operating in actuator space the motion of each cylinder is inherently minimized. To counteract the pendulum-like motion of the hanging payload, a novel anti-swing controller is developed and experimentally verified. The anti-swing controller is able to suppress the motion from the hanging load to increase safety and precision. To tackle the challenges associated with the flexibility of the crane, a deflection compensator is developed and experimentally verified. The deflection compensator is able to counteract both the static deflection due to gravity and dynamic de ection due to motion. Further, the topic of adaptive feedforward control of pressure compensated cylinders has been investigated. A novel adaptive differential controller has been developed and experimentally verified, which adapts to system uncertainties in both directions of motion. Finally, the use of electro-hydrostatic actuators for motion control of cranes has been investigated using numerical time domain simulations. A novel concept is proposed and investigated using simulations.publishedVersio

Performance improvement of a hydraulic active/passive heave compensation winch using semi secondary motor control: Experimental and numerical verification

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Modeling and Control of an Elastic Ship-Mounted Crane Using Variable-Gain Model-Based Controller

This work deals with mathematical modeling and control of elastic ship-mounted cranes which have the Maryland Rigging. The developed model contains three independent inputs to control the vibrations in the plane of the boom; the luff angle is utilized to ensure the controllability of the elastic boom, and the total length of the upper cable in conjunction with the position of its lower suspension point are used to guarantee the controllability of the payload. The disturbance acting on the ship due to sea motions is represented by the rolling displacement of the ship about its center of gravity. The full nonlinear model of the crane is developed and Taylor series is utilized to expand the nonlinear terms about the current equilibrium point which vary with the luff angle and the length of the upper cable. This has led to a linear model with additive nonlinear terms (higher order terms) collected in a separate column vector. Simulation results show that, within a considerable range of pendulation displacements of the payload, the nonlinear model and the linear one obtained by neglecting the nonlinear terms from consideration reflect nearly equivalent responses. Consequently, the linear model is used to design the control system of the crane. The coefficient matrices of this linear model are calculated at the current (instantaneous) equilibrium point, which vary with the luff angle and the length of the upper cable, therefore, a variable-model problem is created and accordingly a variable-gain observer and a variable-gain controller are designed to cover the operation of the crane for all possible equilibrium points in the working space of the crane. The switching between these gains takes place automatically according to the output of a region finder, which uses the measurements of the luff angle and the length of the upper cable to detect the current operating region. A PI-Observer is used to estimate the states and the unknown disturbance force or forces acting directly on the payload; this guarantees that the estimated states converge to their true values even though a nonzero disturbance force acts on the payload. The controller uses the estimated states and the measured roll angle to create the required damping and to compensate for the rolling action of the ship. Stability and performance robustness of the system are ensured for the total working space and also for the expected range of the payload mass. Simulation and experimental results show that the observer can estimate the states and the unknown disturbance acting on the payload very well and the controller can reduce the payload pendulations significantly

Improving Automated Operations of Heavy-Duty Manipulators with Modular Model-Based Control Design

The rapid development of robotization and automation in mobile working machines aims to increase productivity and safety in many industrial sectors. In heavy-duty applications, hydraulically actuated manipulators are the common solution due to their large power-to-weight ratio. As hydraulic systems can exhibit nonlinear dynamic behavior, automated operations with closed-loop control become challenging. In industrial applications, the dexterity of operations for manipulators is ensured by providing interfaces to equip product variants with different tool attachments. By considering these domain-specific tool attachments for heavy-duty hydraulic manipulators (HHMs), the autonomous robotic operating development for all product variants might be a time-consuming process. This thesis aims to develop a modular nonlinear model-based (NMB) control method for HHMs to enable systematic NMB model reuse and control system modularity across different HHM product variants with actuators and tool attachments. Equally importantly, the properties of NMB control are used to improve the high-performance control for multi degrees-of-freedom robotic HHMs, as rigorously stability-guaranteed control systems have been shown to provide superior performance. To achieve these objectives, four research problems (RPs) on HHM controls are addressed. The RPs are focused on damping control methods in underactuated tool attachments, compensating for static actuator nonlinearities, and, equally significantly, improving overall control performance. The fourth RP is introduced for hydraulic series elastic actuators (HSEAs) in HHM applications, which can be regarded as supplementing NMB control with the aim of improving force controllability. Six publications are presented to investigate the RPs in this thesis. The control development focus was on modular NMB control design for HHMs equipped with different actuators and tool attachments consisting of passive and actuated joints. The designed control methods were demonstrated on a full-size HHM and a novel HSEA concept in a heavy-duty experimental setup. The results verified that modular control design for HHM systems can be used to decrease the modifications required to use the manipulator with different tool attachments and floating-base environments

Motion Control of Hydraulic Winch Using Variable Displacement Motors

The paper II is excluded from the dissertation with respect to copyright.To compete in the open market of the offshore crane industry, it is imperative for the manufacturer to continuously improve crane operability. In this context, the crane operability is expressed by means of a so-called weather window. The weather window is computed from the crane characteristics in combination with that of the vessel and the payload to be handled. It returns a set of boundaries for when it is accepted to perform a planned lift, mainly in terms of current sea-state and wind. The most important crane operability characteristics that enter into the computation of the weather window are maximum wire velocity and load capacity. This thesis focuses on how to improve the operability of active heave compensated offshore cranes. Two ways of achieving that goal have been investigated, namely, an improved control strategy and the use of model-based lift planning. The system investigated is the hydraulic active/passive winch system used by National Oilwell Varco. A new control strategy for the system was developed, tested, and implemented. The new strategy utilizes that variable displacement of the hydraulic motors of the active system of the winch drive. The strategy, semi secondary control, gave significant benefits in terms of reduced peak-pressure, increased load capacity, increased wire-speed capacity, and smoother winch performance at low winch speed. The results were validated and verified through simulations and in-field measurements.publishedVersio

Advanced Mathematics and Computational Applications in Control Systems Engineering

Control system engineering is a multidisciplinary discipline that applies automatic control theory to design systems with desired behaviors in control environments. Automatic control theory has played a vital role in the advancement of engineering and science. It has become an essential and integral part of modern industrial and manufacturing processes. Today, the requirements for control precision have increased, and real systems have become more complex. In control engineering and all other engineering disciplines, the impact of advanced mathematical and computational methods is rapidly increasing. Advanced mathematical methods are needed because real-world control systems need to comply with several conditions related to product quality and safety constraints that have to be taken into account in the problem formulation. Conversely, the increment in mathematical complexity has an impact on the computational aspects related to numerical simulation and practical implementation of the algorithms, where a balance must also be maintained between implementation costs and the performance of the control system. This book is a comprehensive set of articles reflecting recent advances in developing and applying advanced mathematics and computational applications in control system engineering

Vision-Based Control of Flexible Robot Systems

This thesis covers the controlling of flexible robot systems by using a camera as a measurement device. To accomplish the purpose of the study, the estimation process of dynamic state variables of flexible link robot has been examined based on camera measurements. For the purpose of testing two application examples for flexible link have been applied, an algorithm for the dynamic state variables estimation is proposed. Flexible robots can have very complex dynamic behavior during their operations, which can lead to induced vibrations. Since the vibrations and its derivative are not all measurable, therefore the estimation of state variables plays a significant role in the state feedback control of flexible link robots. A vision sensor (i.e. camera) realizing a contact-less measurement sensor can be used to measure the deflection of flexible robot arm. Using a vision sensor, however, would generate new effects such as limited accuracy and time delay, which are the main inherent problems of the application of vision sensors within the context. These effects and related compensation approaches are studied in this thesis. An indirect method for link deflection (i.e. system states) sensing is presented. It uses a vision system consisting of a CCD camera and an image processing unit. The main purpose of this thesis is to develop an estimation approach combining suitable measurement devices which are easy to realize with improved reliability. It includes designing two state estimators; the first one for the traditional sensor type (negligible noise and time delay) and the second one is for the camera measurement which account for the dynamic error due to the time delay. The estimation approach is applied first using a single link flexible robot; the dynamic model of the flexible link is derived using a finite element method. Based on the suggested estimation approach, the first observer estimates the vibrations using strain gauge (fast and complete dynamics), and the second observer estimates the vibrations using vision data (slow dynamical parts). In order to achieve an optimal estimation, a proper combination process of the two estimated dynamical parts of the system dynamics is described. The simulation results for the estimations based on vision measurements show that the slow dynamical states can be estimated and the observer can compensate the time delay dynamic errors. It is also observed that an optimal estimation can be attained by combining slow dynamical estimated states with those of fast observer-based on strain gauge measurement. Based on suggested estimation approach a vision-based control for elastic shipmounted crane is designed to regulate the motion of the payload. For the observers and the controller design, a linear dynamic model of elastic-ship mounted crane incorporating a finite element technique for modeling flexible link is employed. In order to estimate the dynamic states variables and the unknown disturbance two state observers are designed. The first one estimates the state variables using camera measurement (augmented Kalman filter). The second one used potentiometers measurement (PI-Observer). To realize a multi-model approach of elastic-ship mounted crane, a variable gain controller and variable gain observers are designed. The variable gain controller is used to generate the required damping to control the system based on the estimated states and the roll angle. Simulation results show that the variable gain observers can adequately estimate the states and the unknown disturbance acting on the payload. It is further observed that the variable gain controller can effectively reduce the payload pendulations. Experiments are conducted using the camera to measure the link deflection of scaled elastic ship-mounted crane system. The results shown that the variable gain controller based on the combined states observers mitigated the vibrations of the system and the swinging of the payload. The presented material above is embedded into an interrelated thesis. A concise introduction to the vision-based control and state estimation problems is attached in the first chapter. An extensive survey of available visual servoing algorithms that include the rigid robot system and the flexible robot system is also presented. The conclusions of the work and suggestions for the future research are provided at the last chapter of this thesis

Proceeding Of Mechanical Engineering Research Day 2016 (MERD’16)

This Open Access e-Proceeding contains a compilation of 105 selected papers from the Mechanical Engineering Research Day 2016 (MERD’16) event, which is held in Kampus Teknologi, Universiti Teknikal Malaysia Melaka (UTeM) - Melaka, Malaysia, on 31 March 2016. The theme chosen for this event is ‘IDEA. INSPIRE. INNOVATE’. It was gratifying to all of us when the response for MERD’16 is overwhelming as the technical committees received more than 200 submissions from various areas of mechanical engineering. After a peer-review process, the editors have accepted 105 papers for the e-proceeding that cover 7 main themes. This open access e-Proceeding can be viewed or downloaded at www3.utem.edu.my/care/proceedings. We hope that these proceeding will serve as a valuable reference for researchers. With the large number of submissions from the researchers in other faculties, the event has achieved its main objective which is to bring together educators, researchers and practitioners to share their findings and perhaps sustaining the research culture in the university. The topics of MERD’16 are based on a combination of fundamental researches, advanced research methodologies and application technologies. As the editor-in-chief, we would like to express our gratitude to the editorial board and fellow review members for their tireless effort in compiling and reviewing the selected papers for this proceeding. We would also like to extend our great appreciation to the members of the Publication Committee and Secretariat for their excellent cooperation in preparing the proceeding of MERD’16

Evolutionary optimisation and real-time self-tuning active vibration control of a flexible beam system

Active vibration control has long been recognised as a solution for flexible beam structure to achieve sufficient vibration suppression. The flexible beam dynamic model is derived according to the Euler Bernoulli beam theory. The resonance frequencies of the beam are investigated analytically and the validity was experimentally verified. This thesis focuses on two main parts: proportional-integralderivative (PID) controller tuning methods based on evolutionary algorithms (EA) and real-time self-tuning control using iterative learning algorithm and poleplacement methods. Optimisation methods for determining the optimal values of proportional-integral-derivative (PID) controller parameters for active vibration control of a flexible beam system are presented. The main objective of tuning the PID controller is to obtain a fast and stable system using EA such as genetic algorithm (GA) and differential evolution (DE) algorithms. The PID controller is tuned offline based on the identified model obtained using experimental input-output data. Experimental results have shown that PID parameters tuned by EA outperformed conventional tuning method in term of better transient response. However, in term of vibration attenuation, the performance between DE, GA and Ziegler-Nichols (ZN) method produced about the same value. For real-time selftuning control, successful design and implementation has been accomplished. Two techniques, self-tuning using iterative learning algorithm and self-tuning poleplacement control were implemented to adapt the controller parameters to meet the desired performances. In self-tuning using iterative learning algorithm, its learning mechanism will automatically find new control parameters. Whereas the self tuning pole-placement control uses system identification in real time and then the control parameters are calculated online. It is observed that self-tuning using iterative learning algorithm does not require accurate model of the plant and control the vibration based on the reference error, but it is unable to maintain its transient performance due to the change of physical parameters. Meanwhile, self-tuning poleplacement controller has shown its ability to maintain its transient performance as it was designed based on the desired closed loop poles where the control system can track changes in the plant and disturbance characteristics at every sampling time. Overall results revealed the effectiveness of both control schemes in suppressing the unwanted vibration over conventional fixed gain controllers