Symmetry Control of Comfortable Vehicle Suspension Based on H∞

Suspension is an important part of intelligent and safe transportation; it is the balance point between the comfort and handling stability of a vehicle under intelligent traffic conditions. In this study, a control method of left-right symmetry of air suspension based on H∞ theory was proposed, which was verified under intelligent traffic conditions. First, the control stability caused by the active suspension control system running on uneven roads needs to be ensured. To address this issue, a 1/4 vehicle active suspension model was established, and the vertical acceleration of the vehicle body was applied as the main index of ride comfort. H∞ performance constraint output indicators of the controller contained the tire dynamic load, suspension dynamic stroke, and actuator control force limit. Based on the Lyapunov stability theory, an output feedback control law with H∞-guaranteed performance was proposed to constrain multiple targets. This way, the control problem was transformed into a solution to the Riccati equation. The simulation results showed that when dealing with general road disturbances, the proposed control strategy can reduce the vehicle body acceleration by about 20% and meet the requirements of an ultimate suspension dynamic deflection of 0.08 m and a dynamic tire load of 1500 N. Using this symmetrical control method can significantly improve the ride comfort and driving stability of a vehicle under intelligent traffic conditions.

A Comparison Study of EDR Estimates from the NLR and NCAR Algorithms

A comparison was made of two eddy dissipation rate (EDR) estimates based on flight data recorded by commercial flights. The EDR estimates from real-time data using the National Center for Atmospheric Research (NCAR) Algorithm were compared with the EDR estimates derived using the Netherlands Aerospace Centre (NLR) Algorithm using quick assess recorder (QAR) data. The estimates were found to be in good agreement in general, although subtle differences were found. The agreement between the two algorithms was better when the flight was above 10,000 ft. The EDR estimates from the two algorithms were also compared with the vertical acceleration experienced by the aircraft. Both EDR estimates showed good correlation with the vertical acceleration and would effectively capture the turbulence subjectively experienced by pilots.

Using In-Vehicle Monitoring Data to Assess Road Conditions of Traffic Flows

Developments in adaptive systems for maintenance and repair of automotive vehicles set the task of monitoring the conditions of their operation. One of the main factors determining these conditions is the type of road surface.The article describes the results of identification of the type (and condition) of the road surface obtained by theoretical and experimental methods based on the analysis of vertical accelerations recorded on the vehicle body.The purpose of research was to provide a possibility of continuous monitoring of the type of road surface on which a vehicle is driving, with the subsequent application of the obtained data to correct maintenance intervals. The results of experiments have shown the dependence of the vertical acceleration of the body on the micro-profile of the road surface. The described experimentally obtained profiles of vertical accelerations refer to different types of road surface in different conditions. For quantitative assessment, it is proposed to calculate the average level of accelerations as an integral average over a certain time interval.The results of the experiments have allowed to substantiate the empirical dependence of the average level of accelerations on speed of a vehicle. Based on this dependence, a method is proposed for recalculating the current values of the average levels of accelerations obtained at different speeds into values adjusted to the base speed to ensure the possibility of their comparison.It is shown that based on the values of average acceleration levels obtained through operation monitoring regarding a previously known type of road surface, it is possible to determine its condition. A short algorithm is formulated for practical implementation and assessment of road conditions of traffic flows. As for hardware, it is proposed not to equip a vehicle with additional sensors but to use operational standard accelerometers as part of in-vehicle emergency call systems, e.g., ERA-GLONASS equipment units.

Continuous Daily Head and Trunk Acceleration Recording for the Assessment of Bone Stimulation in Astronauts

The acceleration of the head and hip along the x-, y-, and z-axis of 14 healthy subjects was recorded during two sessions of 12 consecutive hours. The magnitude, frequency content, and root mean square of the acceleration signals were used to determine the type of physical activity (sitting, standing, walking, etc.) during normal daily life on Earth. The acceleration signal slope (jerk) was also calculated to assess whether these activities were sufficient to maintain bone mineral density. These measurements indicated that the changes in vertical acceleration experienced by our subjects during normal daily life were presumably sufficient to maintain bone mineral density. However, these changes might not be sufficient for postmenopausal women and astronauts during long-term exposure to weightlessness during spaceflight

Method for Determining the Pressure of a Pneumatic Wheel on the Soil

A method for determining the pressure of a pneumatic wheel on the soil is proposed. The method consists in measuring the magnitude of the vertical acceleration of the axles of a self-propelled vehicle, its speed and air pressure in the tire. The research results allow the developers of vehicles fitted with pneumatic wheels to choose rational characteristics of tires and optimal parameters of the oscillatory system of wheeled tractors, which help to reduce soil compaction.

Research on Road Roughness Based on NARX Neural Network

In order to solve the problem of road roughness identification, a study on the nonlinear autoregressive with exogenous inputs (NARX) neural network identification method was carried out in the paper. Firstly, a 7-DOF plane model of vehicle vibration system was established to obtain the vertical acceleration and elevation acceleration of the body, which were set as ideal input samples for the neural network. Then, based on the plane model, with common speed, the road roughness was solved as the ideal output sample of the NARX neural network, and the road roughness of B-level and C-level was identified. The results show that the proposed method has ideal identification accuracy and strong antinoise ability. The relative error of C-level road roughness is larger than that of B-level road roughness. The identified road roughness can provide a theoretical basis for analyzing the dynamic response of expressway roads.

OPERATIONAL BEHAVIOUR OF AN OFFSHORE MULTIPURPOSE SUPPORT VESSEL IN THE EASTERN MEDITERRANEAN SEA

The objective of this work is to analyse the operational behaviour of an offshore multipurpose support vessel designed to operate in the Eastern Mediterranean Sea. First, the seakeeping analysis is performed in a regular wave condition for different heading angles estimating heave and pitch motions through the strip theory. After that, the effects of the vertical acceleration on the bow, occurrence of slamming or hydrodynamic impact of the hull on the surface of the water; wetted deck, occurrence or invasion of water on the deck of the vessel and propeller emersion, motion sickness and wave-induced additional resistance are analysed. The present analysis is extended in an irregular sea condition, and the estimated seakeeping criteria are compared to the acceptable levels. In defining the most suitable operational mode of the offshore support vessels, multi-criteria decision techniques and probabilistic approach are employed to perform an adequate evaluation of the seakeeping performance accounting for different hazardous events through the service life.

Demonstrating the first postulate of relativity in a lift

The first of the two postulates of relativity states that the laws of physics are the same in all inertial reference frames. Often it is assumed that the postulates are mainly concerned with objects moving at a significant fraction of the speed of light. However, the postulates are applicable at all speeds from a snail to a photon. To practically demonstrate the first postulate, the time for a ball to drop a known distance was measured in a stationary and moving lift. An accelerometer app on an iPhone 7 was used to measure the vertical acceleration while the lift travelled between floors and verified that the lift ascended and descended at a constant speed when the ball was dropped. The slow-motion feature of the iPhone 7 (240 fps) was used to capture videos of the falling ball. The number of frames for the ball to fall in a stationary, descending, and ascending lift was respectively 102.4 ± 0.55 , 102.3 ± 1.64 , 99.8 ± 4.21. A t-test revealed no significant difference between these values, confirming the validity of the first postulate. The accelerometer signal was integrated to estimate the average speed of the lift between the bottom and top floor, which was then used to estimate the height difference. An electronic balance placed on the floor of the lift was used to demonstrate the first postulate and the equivalence principle of General Relativity that states that gravitational and inertial mass are equivalent.

Study on the Semiactive Control and Optimal Layout of a Hydropower House Based on Magnetorheological Dampers

With the continuous development of hydropower stations, the capacities and the heads of hydro generator units are increasing, and the plant vibration problem is becoming more and more serious. A numerical simulation method for the vibration reduction control of magnetorheological (MR) dampers suitable for large-scale complex structures was proposed. The method is simple and easy to implement, and the semiactive control of the MR damper could be achieved by adjusting the current switch and size. On the basis of a numerical simulation, a mathematical model for the optimal layout of an MR damper device was established. The objective function was the vertical velocity and the vertical acceleration response of the generator floor. The results showed that the proposed semiactive control numerical simulation method could be applied to the vibration control of the hydropower plant structure, and the vertical velocity and vertical acceleration were reduced by 10.96% and 12.90%, respectively, compared with those without structural vibration control. At the same time, the proposed optimized layout method was effective and feasible, and the damping effect of the MR damper could be effectively improved through the optimized layout.

Research on vibration reduction of semi-active suspension system of quarter vehicle based on time-delayed feedback control with body acceleration

In this paper, the mechanical model of two-degree-of-freedom vehicle semi-active suspension system based on time-delayed feedback control with vertical acceleration of the vehicle body was studied. With frequency-domain analysis method, the optimization of time-delayed feedback control parameters of vehicle suspension system in effective frequency band was studied, and a set of optimization method of time-delayed feedback control parameters based on “equivalent harmonic excitation” was proposed. The time-domain simulation results of vehicle suspension system show that compared with the passive control, the time-delayed feedback control based on the vertical acceleration of the vehicle body under the optimal time-delayed feedback control effectively broadens the vibration absorption bandwidth of the vehicle suspension system. The ride comfort and stability of the vehicle under random road excitation are significantly improved, which provides a theoretical basis for the selection of time-delayed feedback control strategy and the optimal design of time-delayed feedback control parameters of vehicle suspension system.