Disturbance Effect of Pipe Jacking Group Adjacent Excavation on Surrounding Soil

Under the modern and complicated urban environment, clarifying the interaction mechanism and mutual influence mechanism between the urban tunnel and the surrounding environment is of considerable significance to the construction and operation of the tunnel. To understand and grasp the excavation-induced disturbance range and mechanism of adjacent pipeline jacking group on surrounding soils, this paper carries out relevant researches. Based on a case history of a three-hole parallel adjacent jacking pipeline in shallow overburden, a field test and assessment are performed. By setting monitoring points around the monitoring section, the earth pressure and water pressure under different buried depths and different spacing are monitored. For further discussion, the general law of soil disturbance around single-hole, double-hole, and three-hole jacking is investigated, the calculation method of lateral disturbance range and overlapping area range of pipe jacking group is deduced, and the degree of soil disturbance is evaluated as well. The results show that there will be different degrees of disturbance superposition in parallel multihole jacking due to the influence of the spacing, and the disturbance intensity is greatly affected by the parallel distance and buried depth.

Robust trajectory tracking control for autonomous vehicle subject to velocity-varying and uncertain lateral disturbance

Autonomous vehicles are the most advanced intelligent vehicles and will play an important role in reducing traffic accidents, saving energy and reducing emission. Motion control for trajectory tracking is one of the core issues in the field of autonomous vehicle research. According to the characteristics of strong nonlinearity, uncertainty and chang-ing longitudinal velocity for autonomous vehicles at high speed steering condition, the robust trajectory tracking control is studied. Firstly, the vehicle system models are established and the novel target longitudinal velocity planning is carried out. This velocity planning method can not only ensure that the autonomous vehicle operates in a strong nonlinear coupling state in bend, but also easy to be constructed. Then, taking the lateral location deviation minimiz-ing to zero as the lateral control objective, a robust active disturbance rejection control path tracking controller is designed along with an extended state observer which can deal with the varying velocity and uncertain lateral dis-turbance effectively. Additionally, the feedforward-feedback control method is adopted to control the total tire torque, which is distributed according to the steering characteristics of the vehicle for additional yaw moment to enhance vehicle handing stability. Finally, the robustness of the proposed controller is evaluated under velocity-varying condi-tion and sudden lateral disturbance. The single-lane change maneuver and double-lane change maneuver under vary longitudinal velocity and different road adhesions are both simulated. The simulation results based on Matlab/Simulink show that the proposed controller can accurately observe the external disturbances and have good performance in trajectory tracking and handing stability. The maximum lateral error reduces by 0.18 meters compared with a vehicle that controlled by a feedback-feedforward path tracking controller in the single-lane change maneuver. The lateral deviation is still very small even in the double lane change case of abrupt curvature. It should be noted that our proposed control algorithm is simple and robust, thus provide great potential for engineering application.

Study on the Driver/Steering Wheel Interaction in Emergency Situations

Advanced driver assistance systems (ADAS) are becoming increasingly prevalent. The tuning of these systems would benefit from a deep knowledge of human behaviour, especially during emergency manoeuvres; however, this does not appear to commonly be the case. We introduced an instrumented steering wheel (ISW) to measure three components of force and three components of the moment applied by each hand, separately. Using the ISW, we studied the kick plate manoeuvre. The kick plate manoeuvre is an emergency manoeuvre to recover a lateral disturbance inducing a spin. The drivers performed the manoeuvre either keeping two hands on the steering wheel or one hand only. In both cases, a few instants after the lateral disturbance induced by the kick plate occurred, a torque peak was applied at the ISW. Such a torque appeared to be unintentional. The voluntary torque on the ISW occurred after the unintentional torque. The emergency manoeuvre performed with only one hand was quicker, since, if two hands were used, an initial fighting of the two hands against each other was present. Therefore, we propose to model the neuro-muscular activity in driver models to consider the involuntary muscular phenomena, which has a relevant effect on the vehicle dynamic response.

Stiffness Modulation for a Planar Mobile Cable-Driven Parallel Manipulators via Structural Reconfiguration

Mobile Cable-Driven Parallel Manipulators (m-CDPM) are a sub-class of CDPM with greater-capabilities (antagonistic cable-tensioning and reconfigurability) by virtue of mobility of the base-winches. In past work, we had also explored creation of adjustable spring-stiffness modules, in-line with cables, which decouple cable-stiffness and cable-tensions. All these internal-freedoms allow an m-CDPM to track desired trajectories while equilibrating end-effector wrenches and improving lateral disturbance-rejection. However, parameter and configuration selection is key to unlocking these benefits. To this end, we consider an approach to partition task-execution into a primary (fast) winch-tension control and secondary (slow) reconfiguration and joint-stiffness modulation. This would enable a primary trajectory-tracking task together with secondary task-space stiffness tailoring, using system-reconfiguration and joint-stiffness modulation. In this paper, we limit our scope to feasibility-evaluation to achieve the stiffness modulation as a secondary goal within an offline design-optimization setting (but with an eye towards real-time implementation). These aspects are illustrated in the context of a 3-PRP m-CDPM for tracking a desired trajectory within its wrench-feasible workspace. The secondary-task is the directional-alignment and shaping of the stiffness ellipsoid to shape the disturbance-rejection characteristics along the trajectory. The optimization is solved through constrained minimization of a multi-objective weighted cost function subject to non-linear workspace feasibility, and inequality stiffness and tension constraints.

Enhancing lateral dynamic performance of all-terrain vehicles using variable-wheelbase chassis

A six-wheel vehicle chassis scheme with a variable wheelbase is proposed to improve the lateral dynamic performance of vehicles. The yaw moment is varied by changing the wheelbase to enhance the lateral dynamic performance of the vehicle. A vehicle lateral dynamics model is established using this approach. The effects of the wheelbase variation on the lateral yaw rate gain, steering stability, and steering error are analysed via numerical calculations. A strategy for wheelbase variation under different working conditions is proposed to enhance the lateral dynamic performance. In addition, by studying the response of the vehicle to various lateral disturbance forces, it is verified that the wheelbase change can enhance the lateral anti-disturbance capability of the vehicle. The simulation verifies the effectiveness of the wheelbase change strategy under a variety of driving conditions.

Robust H∞ state-feedback control for path following of autonomous ground vehicle based on lateral velocity estimation

A robust [Formula: see text] observer-based static state-feedback controller is designed for the path following of autonomous ground vehicles in this paper. Considering the lateral velocity of vehicle is usually difficult to measure, an observer is designed to estimate the value of lateral velocity first. Then, a robust controller is proposed to cope with the modeling uncertainty and disturbance, such as the variation of road coefficient and lateral disturbance. Numerical simulations using a high-fidelity and full-vehicle model based on a CarSim–Simulink joint platform have verified the effectiveness of the proposed approach.

Instrumented Steering Wheel: Accurate Experimental Characterisation of the Forces Exerted by the Driver Hands for Future Advanced Driver Assistance Systems

The interaction between driver and vehicle is analyzed in the paper. The driver acts on the steering wheel to modify the trajectory and to control the vehicle during panic situations. The knowledge of the forces exerted by the driver at the steering wheel is useful for a better understanding of the driver steering action. The final aim is to inspire the development of haptic steering wheels for better tuning of Advanced Driver Assistance Systems (ADAS). An instrumented steering wheel has been used, which includes two six axis load cells to measure the forces and the moments exerted by the driver hands and six sensors used to measure the grip strength. Two maneuvers have been considered, a moderate speed turn and a kick plate test which simulates a panic situation with an impulsive lateral disturbance. For both of the two considered situations, some common driving behaviors have been highlighted and analyzed. The preliminary results encourage the development of haptic instrumented steering wheels, able to improve ADAS. Actually it seems possible to infer the driver steering purpose before the steering wheel is actually rotated.