Automatic end-of-line tuning for a motion inverter in agricultural tractors

End-of-line tuning is a crucial step for any mass-produced system endowed with automatic controllers. As a matter of fact, due to components tolerances and spreads in the production line, the controller tuning performed on a prototype system is never optimal on the final product. In many industrial applications, though, the end-of-line tuning is performed by human testers, and this does not always guarantee an objective assessment of the closed-loop system quality. This paper proposes a systematic way to design an automatic tuning procedure for a motion-inverter controller in agricultural tractors, which allows to significantly reduce the costs of end-of-line tuning and to obtain a homogeneous manoeuvre quality in all vehicles. The proposed automatic tuning system adapts the controller parameters governing the open-loop phase of the manoeuvre until a predefined manoeuvre quality is achieved. The parameters adaptation phase is guided by an on-line objective assessment of the manoeuvre quality from measured data, which allows to automatically classify the performed manoeuvre with respect to its quality attributes. The effectiveness of the proposed approach is assessed on a prototype vehicle.     

A feasibility study for active remote sensing of atmospheric carbonmonoxide based on differential absorption of infrared radiation alongvertical paths

The authors describe a differential method for estimating mean concentrations of atmospheric molecular components along a quasivertical rectilinear Earth-air path utilizing a transmitter-receiver pair operating at infrared. The choice of a differential method is due to the need to limit calibration problems without utilizing more complex and costly systems such as DIAL, whose capabilities are definitely oversized for this kind of measurement. For this objective, a preliminary selection of the optimal wavenumbers for each molecular species of interest is needed. This is the main issue discussed in this paper, after which the analysis focuses on the effects of the uncertainties on atmospheric parameters that need to be estimated to provide the final mean-concentration estimates. The feasibility study is carried out on carbon monoxide, considered as test species of interest in the reported simulations of atmospheric propagation, based on standard atmospheric models. Technological requirements are finally discussed     

Existence,stability and robustness analysis of limit cycles in hybrid anti-lock braking systems

We investigate the stability and robustness properties of anti-lock braking systems (ABS) based on actuators with on/off dynamics. Namely, we propose a hybrid ABS controller which gives rise to an asymptotically stable limit cycle on the wheel slip. The proposed approach allows to derive exact information on the maximum allowable uncertainty in the measured variables which guarantee the cycle stability. Moreover, a structural stability analysis is performed with respect to different road conditions and to the actuator rate limit.     

Microwave attenuation measurements in satellite-ground links: thepotential of spectral analysis for water vapor profiles retrieval

The authors address the problem of estimating vertical profiles of atmospheric water vapor by means of attenuation measurements simultaneously made at different frequencies along a vertical satellite-ground link. The operating frequencies selected are those around the spectral absorption lines of water vapor at 22.235 GHz. A simulation is presented of multifrequency attenuation measurements, based on an atmospheric propagation model and on radiosonde data providing true profiles of temperature, pressure, and water vapor. The results indicate that such multifrequency measurements are correlated to variations of the vertical profiles of water vapor. It is therefore expected that vertical detail of such profiles depends on number and position of the frequencies utilized     

Robust nonlinear output feedback control for brake by wire control systems

This work proposes a nonlinear output feedback control law for active braking control systems. The control law guarantees bounded control action and can cope also with input constraints. Moreover, the closed-loop system properties are such that the control algorithm allows to detect—without the need of a friction estimator—if the closed-loop system is operating in the unstable region of the friction curve, thereby allowing to enhance both braking performance and safety. The design is performed via Lyapunov-based methods and its effectiveness is assessed via simulations on a multibody vehicle simulator.     

Launch control for sport motorcycles: A clutch-based approach

Launch control is an innovative active system which offers an appealing automatic feature for sport motorcycles. Due to the high power of the engine and to the complexity of the torque transfer dynamics driving a smooth and safe start from a standstill might be difficult for non-expert riders in some working conditions. As such, an active controller capable of safely managing the vehicle acceleration from a standing start might effectively support the rider as far as both safety and performance are concerned. To control such a maneuver, two possible actuators can be employed: the engine throttle and the clutch. This paper illustrates the analysis and the design of a clutch-based launch controller for sport motorcycles, demonstrating that it allows the accurate tracking of an acceleration set-point thanks to a dedicated clutch position controller. Experimental results are presented that demonstrate the effectiveness of the proposed approach.     

Transmission control for power-shift agricultural tractors: Design and end-of-line automatic tuning

This paper addresses the analysis and design of the transmission control system for a high-power power-shift agricultural tractor. Specifically, all the criticalities involved with the correct management of both single clutch and double clutch gear shifts are investigated, and a control system capable of providing good shifting performance in all operating conditions is proposed. Further, to comply with components tolerances and spreads in the production line, an automatic procedure for the end-of-line tuning of the transmission control system is proposed to objectively classify the quality of the gear shift and automatically optimize it. The suitability of the proposed approach is thoroughly tested on an instrumented vehicle.     

Analysis and design of an automatic motion inverter

In this paper, the design of an automatic motion-inverter control system for agricultural tractors has been discussed. The objective of this system is to perform a fully automatic symmetric motion inversion (e.g., from a forward speed of 10 km/h to a reverse speed of -10 km/h). The device used to control the inversion is electro-hydraulic reverser, constituted by two clutches, driven by a proportional electro-hydraulic valve (EVP) and a directional electro-hydraulic valve (EVD). The design of a motion inverter is a nontrivial task, since it is difficult to find a good compromise between speed (the inversion must be completed in a short time) and comfort (bumps and oscillations on the longitudinal speed must be minimized). All the subtasks of the inversion control systems are considered: The design of an inner loop for the control of the EVP current, the open-loop switching strategies, and the design of the outer control loop, which regulates the vehicle speed. The control strategies are experimentally validated, and satisfactory results are obtained.     

Switched Second‐Order Sliding Mode Control with Partial Information: Theory and Application

This paper proposes a novel switched second order sliding mode (S‐SOSM) control strategy in a partial information setting, i.e., when only the sliding variable is accessible for measurements. Such a control approach allows one to deal with systems characterised by different levels of uncertainties associated with different regions of the state space and to accommodate different control objectives in the different regions by switching among appropriate SOSM controllers. The proposed approach is shown to ensure global finite‐time convergence to the origin of the closed‐loop system trajectory. The braking control of two‐wheeled vehicles is considered as a case‐study to test the controller performance.     

Almost Sure Stabilization of Uncertain Continuous-Time Markov Jump Linear Systems

This work deals with the robust Almost Sure (AS) stabilization problem for continuous-time Markov Jump Linear Systems (MJLS). Norm-bounded uncertainties affecting the system state and input matrices are considered. A deterministically testable sufficient condition for robust AS stability is provided which relies on a bound on the 2-norm of the system transition matrix. Such a condition can be profitably employed also to design a robust feedback stabilization strategy. Such feedback design is based on a formulation of the sufficient condition for robust AS stability in terms of an equivalent LMI problem.