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Levelling and stability of agricultural machinery can be required in hilly and mountainous areas. In this study, an electromechanical machine was designed to combine with the omnidirectional levelling control system using BP neural network PID. Firstly, the structure scheme of the electromechanical machine was provided, including an upper working platform, a middle omnidirectional leveling, and a lower tracked driving. The electromechanical leveling system was achieved in the maximum leveling angles of 20° and 25° in the lateral and longitudinal directions, respectively. Secondly, the angle error leveling was used for the omnidirectional leveling system in the control principle. A mathematical model of the servo-electric cylinder was established for the servo motor and transmission. Then, the BP neural network PID algorithm was designed for the leveling control, in which the weight coefficients of the BP neural network were dynamically adjusted, according to the error of body pitch angle. The PID parameters were optimized to improve the leveling speed, accuracy, and stability of the electromechanical machine. Furthermore, a servo-electric cylinder model was established for the BP neural network PID controller in Matlab/Simulink. An integrated mechanical model of the entire machine was established in Adams software. The simulation and experiment were conducted to compare the leveling control performance of improved and classical algorithms using the Matlab/Simulink-Adams co-simulation platform. A classical PID control algorithm was used as a reference. The simulation results show that the better leveling control performance of the BP neural network PID control algorithm was achieved in the lateral leveling control with a tilt angle of 20° and the longitudinal leveling control with a tilt angle of 25°, compared with the classical one. The average reduction in the lateral and longitudinal leveling rise time was 20.09%, and the average reduction in the leveling stabilization time was 18.99%. The steady-state error was controlled within 0.30°. Finally, the static and dynamic tests were conducted on the physical prototype. The static test results show that the BP neural network PID control shared a shorter time of levelling stabilization, smaller maximum inclination overshoot, and lower steady-state error in both lateral 20° and longitudinal 25° levelling control, compared with the PID control, the differences in the leveling stabilization time were 0.5, and 0.4 s, respectively, and the differences in the maximum inclination overshoot were 1.0°, and 0.5°, respectively. The differences in the steady-state error were 0.20°, and 0.15°, respectively, indicating the errors within a small range. The dynamic test results show that the electromechanical working machine was efficiently operated at a speed of 3 km/h on hilly terrain with uneven surfaces when the inclination angle of the fuselage changed significantly. Compared with the PID control, the BP neural network PID control reduced the average stabilization time by 0.5 s for both longitudinal and lateral leveling, resulting in a higher leveling speed. Additionally, the errors in the longitudinal and lateral leveling angles were within ±1.5°, indicating the higher leveling accuracy. The effectiveness of the leveling system and the BP neural network PID control algorithm was verified through experiments. The automatic leveling control of the working platform was realized to fully meet the requirements of levelling performance for the hilly and mountainous operations. The automatic leveling technology of agricultural machinery was avoided the work quality that caused by uneven road surfaces, and large slopes. The finding can also provide a practical reference to explore the structure design and leveling control of the omnidirectional leveling system in the electromechanical working machine, particularly for agricultural machinery. [ABSTRACT FROM AUTHOR]

To obtain the temperature distribution difference between the thermoelectric modules (TEMs) of automotive thermoelectric generator (ATEG) system along the exhaust flow direction, a flow-thermoelectric multi-physics field model was established with considering the exhaust flow and the temperature dependence of thermoelectric material properties. The influence of exhaust temperature and flowrate on the temperature distribution difference was analyzed, and the bench test of ATEG system was performed. The results show that the increasing of exhaust temperature can aggravate the temperature distribution difference between TEMs along exhaust flow direction. When the exhaust temperature is increased from 450 K to 600 K, the relative temperature distribution difference is increased by 105%. The increasing of exhaust flowrate is beneficial to reduce the temperature distribution difference, while the exhaust temperature is the main influence factor on the temperature distribution difference. The accuracy of the multi-physics field mathematical model can reach 97%. [ABSTRACT FROM AUTHOR]

A hybrid electromagnetic suspension control method based on variable time domain model prediction was designed to address the issue of inability to achieve optimal suspension control performance with fixed prediction time domain models under different road surfaces. The simulation analysis was conducted on the relationship between the predictive time domain and the active suspension with the model predictive control effect under external excitations at different frequencies. The optimal predictive time domain was selected for the decelerated and random road surfaces. For the problem of poor active suspension control prediction by the model under random road conditions, the passive dampers were introduced to construct the hybrid electromagnetic suspension, and the passive damping values were optimized and selected. The hybrid electromagnetic suspension control method was designed based on variable time domain model prediction, which could automatically switch the prediction time domain according to the driving surfaces. The simulation analysis results by MATLAB show that the designed control method can effectively improve vehicle ride comfort and handling stability under complex road conditions. [ABSTRACT FROM AUTHOR]

To solve the problems of vehicle body attitude change and vertical vibration due to vehicle driving conditions and uneven road surface, a control method for vehicle semi-active suspension was designed based on magnetorheological semi-active suspension system, which was composed of attitude compensation control algorithm, magnetorheological damper control algorithm and accurate state observer design method. The vehicle attitude control and the suspension vertical vibration control were considered in the attitude compensation control algorithm, and the equivalent damping control of the magnetorheological semi-active suspension system was carried out by the magnetorheological damper control algorithm to optimize the body attitude and improve the vehicle comfort. To estimate the required speed signals more accurately, the actual equivalent damping was used to update the parameter matrices in the observer in real time, and the accurate state observer was constructed. The simulation and experimental results show that body acceleration, pitch angle acceleration and roll angle acceleration can be improved effectively by the proposed control algorithm, and RMS values of them are respectively reduced by 14.03%, 18.26% and 21.39%, which implies the effectiveness of the designed control algorithm. [ABSTRACT FROM AUTHOR]

Compared with the passive suspension, the hydraulic electrical energy-regenerative suspension can not only recycle the energy dissipated by the suspension, but also improve the dynamic performance of vehicle, which has attracted extensive attention of scholars at domestic and abroad. However, the most of research focuses on the analysis of energy-feedback characteristics，without considering how to improve the dynamic performance of vehicles adaptively according to complex road conditions while restoring energy considered. In addition, the ride comfort and handling stability of vehicle are mutually constrained, and the contradiction between them is still prominent under the passive mode. In order to meet the optimal performance of hydraulic electrical energy-regenerative suspension during the global operating condition, a hydraulic electrical energy-regenerative suspension with 3 working modes focusing on comfort, sport and comprehensiveness modes was designed to regenerate vibration energy while improving the ride comfort and handling stability of the vehicle in this paper. The road excitation frequency was chosen as the suspension mode switching threshold. The hydraulic electrical energy-regenerative shock absorber was composed of a hydraulic cylinder, a hydraulic rectifier bridge, a hydraulic motor, 2 accumulators, the hydraulic pipeline, a rotary motor, etc., wherein the hydraulic rectifier bridge consisted of 4 one-way valves. The DC-DC converter was introduced into the suspension energy-regenerative circuit. Based on this, the damping force formula of the shock absorber was derived. The double loop semi-active control scheme consisting of skyhook-groundhook control and fuzzy PID control was designed. The semi-active control of the hydraulic electrical energy-regenerative suspension was achieved based on the energy-regenerative circuit. The DC-DC converter could work in both boost and buck modes. The duty cycle of the MOS tube switching signal in the DC-DC converter was adjusted real time to change the damping force of the damper. Moreover, the Kalman Filter algorithm was introduced to accurately obtain the suspension state variables to track the ideal damping force. The first-order zero-crossing detection method was introduced to identify the main frequency of the road input, which was used as the switching threshold of each suspension working mode. The simulation results showed that the hydraulic electrical energy-regenerative semi-active suspension could switch the working mode adaptively according to the road frequency, and improve the vehicle dynamic performance effectively than the single mode control of semi-active suspension while regenerating energy. The proposed hydraulic electrical energy-regenerative suspension combined with road frequency self-adaption could coordinate suspension dynamic performance with energy-regenerative characteristics. The vehicle body acceleration in the comfort mode was reduced by 13.75% compared with that of the single mode control suspension, and the tire dynamic load was reduced by 17.76% in the sport mode. To verify the effectiveness of the simulation, a bench test was performed. The deviations of the PTP(peak-to-peak) value of test and simulation data of vehicle body acceleration were 1.36%, 15.72%, 4.86%, and 13.6%, respectively, and the ones of the tire dynamic load were 9.34%, 13.62%, 7.82%, and 15.47%, respectively. The errors between the test and simulation results was within 16%, which verified the correctness of the simulation results and the feasibility of the semi-active suspension system. The study provides an important reference for the performance upgrade of the hydraulic electrical energy-regenerative suspension. [ABSTRACT FROM AUTHOR]

To predict the dynamic characteristics of the thermoelectric generator (TEG) system, a transient computational fluid dynamics (CFD) model for solving the temperature field distribution of TEG system and an analysis model for investigating the transient response characteristics of TEG modules were established based on COMSOL Multiphysics. A hybrid transient CFD-analysis model was proposed and validated through transient experiments. The results show that due to the thermal inertia effect, the conversion efficiency of TEG system exhibits momentary peak value. Compared to the transient fluctuations of exhaust gas temperature and mass flow rate, there is time lag in the hot and cold side temperatures of the thermoelectric semiconductor. Under the highway fuel economy test (HWFET) cycle conditions defined by the U.S. Environmental Protection Agency, by the transient model, the average output power and the average conversion efficiency of the entire TEG system are solved with 35.63 W and 3.40%, respectively. The average error of the transient model's output voltage is 6.41%. By the proposed model, the transient response characteristics of the TEG system under transient thermal source excitation can be predicted with high accuracy and short computation time. [ABSTRACT FROM AUTHOR]

Stability of body inclination, work quality and safety can be required during agricultural machinery operation in hilly and mountainous areas. In this study, an omnidirectional leveling system was designed for the crawler work machine. A structural scheme was also proposed with an articulated omnidirectional leveling system using a “three-layer frame”. The leveling hydraulic circuit was provided for the working principle of the omnidirectional leveling system. Secondly, a sensitivity analysis was conducted on the omnidirectional leveling performance, including the key structural parameters LAE, LBC, LCD, LHO, LIJ, and LIJ. The results showed that the displacement of the lateral leveling cylinder increased with the increase of LAE and LCD, whereas, decreased with the increase of LBC. The displacement of the longitudinal leveling cylinder increased with the increase of LJK and LIJ, while decreasing with the increase of LHO. The average thrust of the lateral leveling hydraulic cylinder decreased with the increase of LAE and LCD, but the leveling time increased. By contrast, the average thrust of the longitudinal leveling hydraulic cylinder increased with the increase of LJK, but the leveling time decreased. A multi-objective genetic algorithm (GA) was designed to optimize the key structural parameters, taking the key structural parameters of the omnidirectional leveling system as the optimization variables, and the average thrust of the hydraulic cylinder and leveling time as the optimization objectives. Then, the overturning model was established for the omnidirectional leveling crawler work machine. The overturning stability of the whole machine was verified to analyze the static lateral limit overturning angle, static longitudinal limit overturning angle, and dynamic limit driving speed of the crawler work machine. The lateral and longitudinal limit overturning angles of the unleveled crawler work machine were 43.6˚, and 60.7˚, respectively, whereas, they were 46.7˚, and 68.9˚, respectively, after leveling. The lateral/longitudinal limit overturning angles after leveling increased by 7.1% and 13.5%, respectively. There was an increase in the maximum driving slope of the crawler work machine, compared with the non-leveling one. The limit driving speed of the crawler work machine to do circular motion on a flat road surface was 4.3m/s, when the radius of circular motion was 2m. Once the slope was 20˚, the dynamic limit driving speeds were 2.9 and 3m/s for the unleveled and omnidirectional leveling crawler work machine, respectively, which increased by 3.4%. Finally, an omnidirectional leveling performance test was conducted to verify the system effectiveness. The test results indicated that the lateral and longitudinal leveling times were 3.4 and 3.6s, respectively, under static testing. By contrast, the maximum body inclination angle of the omnidirectional leveling crawler work machine decreased outstandingly and then quickly leveled under dynamic testing. The body inclination angle can be maintained within ±1.5˚ on the flat road and after leveling, which fully met the performance requirements of hilly and mountainous areas. [ABSTRACT FROM AUTHOR]

To solve the problems of existing lag angle between the phase combustion parameters identified by vibration signal and cylinder pressure signal and of existing different lag angles under different working conditions, the parameters for characterizing the high-frequency harmonics of in-cylinder pressure signal were investigated. The S-transformation of cylinder pressure was analyzed to determine the range of frequency distribution caused by the combustion excitation. The one-dimensional simulation model of the single-cylinder diesel engine was established to analyze the maximum pressure. The results show that the maximum pressure rise rate, the peak pressure, the ratio of the maximum pressure rise rate to the interval between the start of combustion and the maximum pressure rise rate and the interval between the start of combustion and the peak pressure are approximately linear to the high frequency energy of the cylinder pressure signal. In the vibration velocity signal, the corresponding parameters of pir A'B',pirA',B'/δφ'and δθ can be used to represent the high-frequency energy. A reference is provided for correcting lag angle based on characteristic parameters of vibration velocity signals. [ABSTRACT FROM AUTHOR]

To solve the contradictory problem of search time-consuming and path accuracy by A * algorithm for the path planning of current intelligent vehicles , the hybrid SA algorithm was proposed to ensure efficiency of search time-consuming and improve path accuracy in path planning. Based on the traditional connective mode of node , a new connective mode of node and S algorithm were proposed , and the switch mechanism of hybrid SA algorithm was designed to obtain suboptimal paths in shorter time. The single map simulation experiments of path planning were conducted. The SA algorithm was verified that the paths of repeated programming were consistent , and the search time-consuming deviations had certain limitations in different single maps. The universal simulation experiments were also conducted , and the performance indexes of SA algorithm and four-connection A * algorithm were compared and analyzed. The results show that compared with A* algorithm by four-connection nodes , SA algorithm can improve the path accuracy and ensure the advantages of search time-consuming under the global working condition , especially for the low percentage obstacle map , the effect is more obvious. [ABSTRACT FROM AUTHOR]

To improve the generating precision of driving signal in multiple-input multiple-out (MIMO) linear random vibration test system, a new method called Cholesky decomposition(CD) filter based on white noise is proposed according to the matrix decomposition theory in view of the nonnegative definite Hermite characteristic of driving powr spectral density(PSD). The lower triangular matrix with particular frequency response transfer characteristics is constructed. A series of independent white noises are passed through the system, and the multiple stationary random signals with articipative coherence performance, phases and self-PSD are obtained. A two-input two-output simulation system based on a cantilever beam is established to verify the effectiveness of the proposed method. The mixed reference spectrum including board and narrow random signals is set and the results between the traditional time-frequency transformation method based on Fourier transform and the new method are compared. The results show that the new method has high accuracy in the self-spectrum and cross-spectrum, and can meet the technical requirements of engineering application, thus improving the effect of random vibration environment test control. [ABSTRACT FROM AUTHOR]

To coordinate the contradiction between improving the dynamic performance and reducing the energy consumption of the system, the hybrid electromagnetic active suspension (HEMAS) was used as a potential solution. Based on the improved skyhook control strategy, the general energy-saving mechanism of HEMAS was realized compared with linear electromagnetic active suspension (LEMAS). Taking the passive suspension and the LEMAS as comparison objects, a comparison bench test was carried out. The test results show that compared with passive suspension, the RMS of vehicle acceleration and suspension dynamic deflection of the HEMAS are respectively reduced by 23.35% and 14.97% with good tire grounding ability. Compared with LEMAS, the electric power consumption of the HEMAS is reduced by 70.60% for the same dynamic performance, which verifies the superiority of HEMAS with consideration of the system dynamic performance and energy consumption. [ABSTRACT FROM AUTHOR]