Dynamic Simulation Platform Research Articles

Control Strategy and Simulation of Four-wheel-hub Vehicles Torque Distribution on Bisectional Road

In this paper, the driving force distribution control strategy of distributed drive vehicle for four wheel hub motor is studied. With the idea of double layer control. The vehicle dynamics simulation platform of the independent driving vehicle of the wheel motor is built. The influence of vehicle stability and dynamic performance is analyzed when the vehicle is running on bisectional road. The torque control strategy of four wheel hub motors based on sliding mode control was designed. Simulation results show that: When the vehicle is running on bisectional road, the control strategy can ensure the vehicle stability and improve the dynamic performance of the vehicle.

Dynamic simulation studies for boiler draft

Increasingly strict NOx and SOx emission limits demand the fossil and fuel fired power industry to upgrade their gas treatment system with Flue Gas Desulphurization (FGD) and Selective Catalytic Reduction (SCR) equipment. To compensate for the additional pressure drop the new equipment introduces into the flue gas path due, the existing induced draft (ID) fans need to be replaced with higher head fans or new booster fans. This requires new duct work to connect the equipment. While the new duct work can be designed considering the new operating conditions, the existing duct work may not have been designed with these unanticipated changes and hence may be at risk of implosion and mechanical damage. This paper examines how a high-fidelity process and control model of the air, furnace, and flue gas path of a coal fired power plant is developed for a transient analysis study by using a dynamic simulation platform – DYNSIM. Also included is a case-study which evaluated the processes dynamics of a 225MW unit. The objective of the study was to ensure design safety by evaluating the process dynamics of the unit prior to retrofitting the unit’s draft system. The model, validated with historian data and design data, was used to evaluate the air and flue gas system pressure fluctuations in response to upsets such as fan trips and runaways. The resulting pressures were then available for use as a basis for the duct work design.

Coupled multimodal fluid-vehicle model for analysis of anti-slosh effectiveness of longitudinal baffles in a partially-filled tank vehicle

An efficient model is formulated for analysis of a coupled fluid slosh-vehicle dynamic system to study the effects of different baffle designs on directional dynamic performance of a partially-filled tank vehicle. A multimodal model of fluid sloshing within a baffled cylindrical tank is initially formulated using potential flow equations and linearized free-surface boundary condition considering maneuver-induced vehicle motions along the lateral, vertical and roll axes. Natural slosh modes/frequencies, hydrodynamic coefficients and Stokes-Joukowski potential associated with the multimodal model are then obtained by solving the eigenvalue problem of free fluid sloshing using a higher order boundary element method. Significant improvement in computational time is achieved by reducing the generalized eigenvalue problem to a standard one involving only the velocity potentials on the half free-surface length using the zoning method. The hydrodynamic force and moment obtained from the multimodal model are subsequently coupled with the TruckSim vehicle dynamic simulation platform through a MATLAB/Simulink model to obtain dynamic responses of a partially-filled tank vehicle with and without baffles under step-turn and double-lane change maneuvers. Two different designs of longitudinal baffles are considered: bottom- and top-mounted baffles. The validity and efficiency of the present boundary element method is demonstrated by comparing the results with those obtained using the boundary element method employing linear elements. The effective mass moment of inertial of the fluid in a clean-bore tank is also obtained as a function of fill ratio and compared with the reported analytical solutions for a half-full tank to further verify the model. The results suggest that directional dynamic responses of partly-filled tank vehicles can be efficiently analyzed using the coupled multimodal slosh-vehicle models with significantly lower computational effort than the methods employing computational fluid dynamic (CFD) fluid slosh models. The results further reveal that top-mounted baffles are most effective in suppressing the fluid slosh force under more likely loading conditions in road tankers.

A real-time, high fidelity dynamic simulation platform for hexapod robots on soft terrain

Dynamic simulation is an important aspect of legged robotic research, which is essential for its design and control. However, the dynamics of the interaction between a soft terrain and a deformable leg (e.g., a spring) is hardly taken into account. In this paper, a high-fidelity, faster-than-real-time simulation system for hexapod robots has been developed based on Vortex. Foot-terrain interaction mechanics and flexible mechanical system are taken into account in order to improve the simulation precision. A general foot-terrain interaction model is presented based on terramechanics. Pseudo-rigid-body method is used to simulate the flexibility of the robot. A speed test shows that the simulation system is capable of real-time or faster simulation. The simulation system's fidelity was validated using two hexapod robots, which is found to be greater than 90%.

Flight modeling and simulation for dynamic soaring with small unmanned air vehicles

The design of guidance and control strategies is a promising study trend of dynamic soaring for small unmanned aerial vehicles, for which the flight modeling and simulation specifically for soaring-capable unmanned aerial vehicles is significant and necessary. The aim of this paper is to propose a flight simulation platform for dynamic soaring. In order to do so, firstly, two different sets of equations of motion of small unmanned aerial vehicles have been derived and their characteristics are compared: one is expressed in body-fixed frame and the other in air-relative flight path frame. Secondly, the latter set is used for energy analysis to maximize energy gain while climbing and diving and minimize energy cost during turning in dynamic soaring. While the former serves to build the dynamic soaring simulation platform, in which a piecewise trajectory-based guidance and control strategy according to the energy analysis is proposed tracking the optimum climb and bank angles and traveling toward desired directions. Simulation results indicate that the unmanned aerial vehicles can perform dynamic soaring toward various directions in different wind fields, follow asymptotically the typical straight-line and circular-orbit paths by repeating soaring cycles.

A model-based adaptive method for evaluating the energy impact of low delta-T syndrome in complex HVAC systems using support vector regression

Low delta-T syndrome refers to the situation where the measured differential temperature of the overall terminal air-handling units is much lower than the normal value expected. It widely exists in the existing heating, ventilating, and air-conditioning systems and results in increased energy consumption. This paper presents a model-based method to evaluate the energy impact on the chilled water pumps due to the low delta-T syndrome in a complex chilled water system. When the low delta-T syndrome occurs, the chilled water pumps would deviate from their normal working conditions with increased power consumption. Models are developed to predict the reference benchmarks of the chilled water pump power based on the current cooling load, control rules, and preset set-points. The energy impact on the chilled water pumps can be determined by comparing the measured current pump power with the predicted benchmark. Support vector regression method is introduced for predicting the chilled water flow rate of the overall terminal units. Adaptive concept is employed to enhance the prediction accuracy of the overall pressure drop of the hydraulic water network under various working conditions. The proposed method is tested and validated in a dynamic simulation platform built based on a real complex heating, ventilating, and air-conditioning system. Results show that the proposed method can accurately evaluate the impact of the low delta-T syndrome on energy consumption of the chilled water pumps. Practical application: Low delta-T syndrome widely exists in existing HVAC systems and results in increased energy consumption. This paper presents a model-based method for practical applications in assessing the energy impact on the chilled water pumps due to the low delta-T syndrome in a complex chilled water system. When the low delta-T syndrome occurs in a system, this method can be used to predict the reference benchmark of energy use of chilled water pumps based on the measured cooling load profiles, the control rules used, and the preset set-points. The energy impact can be determined by comparing the measured actual energy consumption with the predicted benchmark. The evaluation results could help the operators to conveniently monitor the energy performance of the chilled water distribution system as well as to judge whether or not taking measures to identify and correct the related faults that result in the low delta-T syndrome.

A wolf pack hunting strategy based virtual tribes control for automatic generation control of smart grid

This paper proposes a novel electric power autonomy to satisfy the requirement of power generation optimization of smart grid and decentralized energy management system. A decentralized virtual tribes control (VTC) is developed which can effectively coordinate the regional dispatch centre and the distributed energy. Then a wolf pack hunting (WPH) strategy based VTC (WPH-VTC) is designed through combining the multi-agent system stochastic game and multi-agent system collaborative consensus, which is called the multi-agent system stochastic consensus game, to achieve the coordination and optimization of the decentralized VTC, such that different types of renewable energy can be effectively integrated into the electric power autonomy. The proposed scheme is implemented on a flexible and dynamic multi-agent stochastic game-based VTC simulation platform, which control performance is evaluated on a typical two-area load–frequency control power system and a practical Guangdong power grid model in southern China. Simulation results verify that it can improve the closed-loop system performances, increase the utilization rate of the renewable energy, reduce the carbon emissions, and achieve a fast convergence rate with significant robustness compared with those of existing schemes.

A lightweight shoulder prosthesis with antagonistic impact-absorbing hybrid actuation for bimanual activities of daily living

In developing a shoulder prosthesis, in addition to appropriate payload and range of motion under the constraints of weight and shape, impact absorption is very important for safe use. Hybridization of two different actuators (pneumatic elastic actuators with the features of lightness and intrinsic visco-elasticity, and servo motors that have stable torque and a large range of motion in combination with an antagonistic mechanism) was employed to achieve the development of the shoulder prosthesis. A two-link, two-degree-of-freedom arm was used to test the different hybridization configurations in order to investigate the impact absorption. A dynamic simulation platform based on four bimanual activities of daily living was established to obtain the required range of motion and torque for joints of a two-link, four-degree-of-freedom arm. The number of pneumatic elastic actuators required and the dimension of the antagonistic mechanism mechanical structures were optimized using the dynamic simulation platform. The best configuration of the two types of actuators was determined using the dynamic simulation based on the impact absorption results and other criteria. Moreover, a simplified prototype driven by hybrid actuation was made. It was shown that the pneumatic elastic actuator joint could improve impact absorption, and the actuator configuration of shoulder prostheses is activity of daily living dependent. The prototype could reproduce a certain activity of daily living motion, indicating its feasibility in daily living.

Coordinated Resolved Motion Control of Dual-Arm Manipulators with Closed Chain

When applied to some tasks, such as payload handling, assembling, repairing and so on, the two arms of a humanoid robot will form a closed kinematic chain. It makes the motion planning and control for dual-arm coordination very complex and difficult. In this paper, we present three types of resolved motion control methods for a humanoid robot during coordinated manipulation. They are, respectively, position-level, velocity-level and acceleration-level resolved motion control methods. The desired pose, velocity and acceleration of each end-effector are then resolved according to the desired motion of the payload and the constraints on the closed-chain system without consideration of the internal force. Corresponding to the three cases above, the joint variables of each arm are then calculated using the inverse kinematic equations, at position-level, velocity-level or acceleration-level. Finally, a dynamic modelling and simulation platform is established based on ADAMS and Matlab software. The proposed methods are verified by typical cases. The simulation results show that the proposed control strategy can realize the dual-arm coordinated operation and the internal force of the closed chain during the operation is controlled in a reasonable range at the same time.

Robust Model Predictive Control for Path Tracking of a Tracked Vehicle with a Steerable Trailer in the Presence of Slip

Abstract: In comparison to general autonomous robots, high precision guidance of farm vehicles becomes more complex and challenging as these vehicles are inevitably subjected to significant slip caused by very rough and unsteady terrain which is sometimes undulating. Therefore, it is essential to design controllers that have the capability to react to significant and uncertain disturbances. This paper presents a robust model predictive controller for path tracking of a tracked vehicle towing a steerable trailer in the presence of unknown but bounded disturbances. Based on kinematics and a virtual spring, a virtual error vector model with slip is used to model path offset and orientation offset for the tracked vehicle and the trailer. An adaptive min-max model predictive control method is proposed to guarantee robustness and accuracy in the path tracking. Finally, the proposed controller is compared with a min-max model predictive controller and a sliding mode controller in a realistic dynamic simulation platform. The results prove that the proposed adaptive min-max model predictive controller provides the required accuracy and robustness in the presence of slip.

Numerical investigation of cable breakage events on long-span cable-stayed bridges under stochastic traffic and wind

Cable breakage (loss) events can be disastrous to cable-stayed bridges because of potential risks of progressive collapse following the initial failure of stay cables. To avoid turning a cable-breakage hazard into a disaster, it is important to rationally assess the risk through accurately predicting the nonlinear dynamic behavior of the bridge subjected to various types of cable-loss events. With a recently developed advanced finite element (FE)-based nonlinear dynamic simulation platform, a comprehensive numerical investigation of cable-loss incidents on a long-span cable-stayed bridge is conducted by focusing on post-breakage performance. Parametric studies are carried out to evaluate the impacts from various important parameters related to cable-breakage process and service loads from stochastic traffic and wind. Several parameters associated with cable-breakage processes, such as the breakage duration, time-transient curve and initial state, are found to influence the dynamic performance of the bridge notably. The results also indicate that service traffic and wind loads as well as complex coupling effects with the bridge are important to the bridge response following cable-loss events. In the final part of the study, response envelope analysis is made and a comparative investigation is also conducted between the results from the advanced FE-based nonlinear dynamic approach and those from the equivalent static approach as suggested by the Post-Tensioning Institute (PTI).

Dynamic Simulation System Using DOF Picking Robot

A visualized dynamic simulation platform of picking robot based on OpenGL and Matlab is established in or- der to verify the validity of kinematics analysis and visually reflect the motion process.The robot kinematic model is es- tablished with D-H method and the forward kinematic solution for the robot is obtained. The inverse kinematic solution is solved by using the simplified inverse transformation method according to the operation features of the robot. Solidworks is adopted to set up 3D robot model, which is transformed through Deep Exploration into cpp formatted files that can be recognized by OpenGL. Visualized simulation verification is conducted on the forward and the inverse kinematic solution and the grabbing motion of the manipulator are conducted on the simulation platform based on VisualC++6.0 and OpenGL. Track planning is carried out for each of the manipulator joints by means of Matlab Robotics Toolbox. It is il- lustrated by the simulation results that the kinematic model established by D-H approach reflects the real motion condi- tions of the robot, and both the forward and inverse kinematic solutions are correct.

A novel multi-agent decentralized win or learn fast policy hill-climbing with eligibility trace algorithm for smart generation control of interconnected complex power grids

This paper proposes a multi-agent smart generation control scheme for the automatic generation control coordination in interconnected complex power systems. A novel multi-agent decentralized win or learn fast policy hill-climbing with eligibility trace algorithm is developed, which can effectively identify the optimal average policies via a variable learning rate under various operation conditions. Based on control performance standards, the proposed approach is implemented in a flexible multi-agent stochastic dynamic game-based smart generation control simulation platform. Based on the mixed strategy and average policy, it is highly adaptive in stochastic non-Markov environments and large time-delay systems, which can fulfill automatic generation control coordination in interconnected complex power systems in the presence of increasing penetration of decentralized renewable energy. Two case studies on both a two-area load–frequency control power system and the China Southern Power Grid model have been done. Simulation results verify that multi-agent smart generation control scheme based on the proposed approach can obtain optimal average policies thus improve the closed-loop system performances, and can achieve a fast convergence rate with significant robustness compared with other methods.

Transient Simulation of High Temperature High Pressure Solar Tower Receiver

A solar receiver undergoes frequent transients events and the nature of these transient events is very different from conventional thermal power plants. The SRSG (Solar Receiver Steam Generator) operates during the day when heat from the sun is available and is shut-down during the night. Along with the daily start-up and shut-down, italso undergoes various other transient events including short or long cloud events followed by hot-start, partial load transient during light cloud events, cold start-up transients(after extended shut-down events) and failure modes. The operation and control strategy for the SRSG should incorporate safe operation during all the transient events while optimizing on power generation. It is therefore important to model the SRSG and study the dynamic response of the SRSG under various transient conditions. This paper discusses modeling of Alstom SRSG using the APROS dynamic simulation platform. The paper describes in detail various components of high pressure, high temperature SRSG along with the need for transient modeling during the design phase. It provides details of various transient events that were simulated along with a discussion on the simulation results. The paper highlights the optimized modes of operation procedure developed using transient modeling along with control strategies.

Multiagent Stochastic Dynamic Game for Smart Generation Control

AbstractThis paper proposes a multiagent (MA) smart generation control (SGC) scheme for the coordination of automatic generation control (AGC) in power grids with system uncertainties. Under the control performance standards, SGC will undergo a non-Markov random process, of which the optimal solution can be resolved online by the reinforcement learning. Therefore, an MA decentralized correlated equilibrium Q(λ)-learning algorithm, and an MA stochastic dynamic game-based SGC simulation platform (SGC-SP) have been proposed for its implementation, which can achieve AGC coordination in a highly uncertain environment resulting from the increasing penetration of renewable energy. Single-agent Q-learning, Q(λ)-learning, R(λ)-learning, and proportional integral control are implemented and embedded in SGC-SP for the control performance analysis. Two case studies on both a two-area power system and the China Southern Power Grid model have been done, which verify its effectiveness and scalability.

A system-level fault detection and diagnosis method for low delta-T syndrome in the complex HVAC systems

Low delta-T syndrome widely exists in the existing air-conditioning systems and results in increased energy consumption. This paper presents a system-level fault detection and diagnosis method (FDD) to detect and diagnose the low delta-T syndrome resulted from the performance degradation of AHUs system and plate heat exchanger system in a complex HVAC system. Performance indices are introduced to characterize the health status (normal or faulty) of the system. Reference models are developed to generate the benchmarks of the performance indices under fault-free conditions. In order to mitigate the impact of the model fitting uncertainty of the reference models and the measurement uncertainty of the performance indices, adaptive thresholds are adopted using t-statistic approach to identify the health conditions of the performance indices. The proposed method was validated in a dynamic simulation platform built based on a real complex HVAC system studied. The results show that the proposed FDD strategy can successfully detect the low delta-T syndrome, identify the related faults and quantitatively evaluate of the faults severity.

A topological approach to using cables to separate and manipulate sets of objects

In this paper we study the problem of manipulating and transporting multiple objects on the plane using a cable attached at each end to a mobile robot. This problem is motivated by the use of boats with booms in skimming operations for cleaning oil spills or removing debris on the surface of the water. The goal in this paper is to automate the task of separating the objects of interest from a collection of objects by manipulating them with cables that are actuated only at the ends, and then transporting them to specified destinations. Because the cable is flexible, the shape of the cable must be explicitly modeled in the problem. Further, the robots must cooperatively plan motions to achieve the required cable shape and gross position/orientation to separate the objects of interest and then transport them as specified. The theoretical foundation for the problem is derived from topological invariants, homology and homotopy. We first derive the necessary topological conditions for achieving the desired separation of objects. We then propose a distributed search-based planning technique for finding optimal robot trajectories for separation and transportation. We demonstrate the applicability of this method using a dynamic simulation platform with explicit models of the cable dynamics, the contact between the cable and one or more objects, and the surface drag on the cable and on the objects. We also demonstrate the working of the proposed algorithm on an experimental platform consisting of a system of two cooperating autonomous surface vessels and stationary/anchored objects.

Constrained [formula omitted] control for road vehicles after a tire blow-out

Sudden tire blow-out of a road vehicle is a hazardous situation and frequently cited as the cause of a crash and fatality on the highway. As the uncertainties/disturbances caused by a tire blow-out are difficult to be measured or estimated, this study proposes a novel constrained H∞ coordinated control approach for the path-following and driving stability problem of the road vehicles after a tire blow-out. Simulation results and analyses for a variety of driving scenarios are conducted, based on a co-simulation between the proposed vehicle controller and vehicle dynamics simulation platform veDYNA. The dynamic analyses clearly demonstrate the effectiveness of the proposed coordinated controller in improving vehicle stability, as well as the robustness of the controller against the uncertainties/disturbances caused by a tire blow-out.

Sensitivity analysis of macro-parameters in the system design of net zero energy building

The rapid growth of building energy has imposed increasing pressure on environmental protection. Net zero energy building (NZEB) is widely considered to be an effective solution. Various macro-parameters in a NZEB have different impacts on system design and very few studies have investigated such impacts in a NZEB. Therefore, a systematic sensitivity analysis of macro-parameters in a NZEB has been conducted in this study. Differential sensitivity analysis, a local sensitivity analysis method, is performed on a constructed dynamic simulation platform to study the impacts of each macro-parameter on the sizes of key NZEB systems. The systems include heating, ventilation and air-conditioning (HVAC) system, renewable energy system and energy storage system. The influence coefficient of each parameter is calculated to quantify its sensitivity impacts. Meanwhile, an exhaustive search approach is proposed to minimize the overall initial investment cost of the renewable energy system and storage system. The study results are valuable to help designers improve NZEB system design through carefully selecting more accurate design parameters especially those identified with heavy sensitivity impacts. The study also provides a method to optimize the initial investment cost of systems in a NZEB.

Dynamic Model of a Multibending Soft Robot Arm Driven by Cables

The new and promising field of soft robotics has many open areas of research such as the development of an exhaustive theoretical and methodological approach to dynamic modeling. To help contribute to this area of research, this paper develops a dynamic model of a continuum soft robot arm driven by cables and based upon a rigorous geometrically exact approach. The model fully investigates both dynamic interaction with a dense medium and the coupled tendon condition. The model was experimentally validated with satisfactory results, using a soft robot arm working prototype inspired by the octopus arm and capable of multibending. Experimental validation was performed for the octopus most characteristic movements: bending, reaching, and fetching. The present model can be used in the design phase as a dynamic simulation platform and to design the control strategy of a continuum robot arm moving in a dense medium.