Development of Look-Ahead Controller Concepts for a Wheel Loader Application

Abstract

-This paper presents two conceptual methods, based on dynamic programming, for onestep look-ahead control of a Continuously Variable Transmission (CVT) in a wheel loader. The first method developed, designated Stochastic Dynamic Programming (SDP), uses a statistical load prediction and stochastic dynamic programming for minimizing fuel use. The second method developed, designated Free-Time Dynamic Programming (FTDP), has vehicle speed as a state and introduces a fixed 0:1 s delay in the bucket controls in a combined minimization of fuel and time. The methods are evaluated using a set of 34 measured loading cycles, used in a 'leave one out' manner. The evaluation shows that the SDP method requires about 1=10th of the computational effort of FTDP and has a more transparent impact of differences in the cycle prediction. The FTDP method, on the other hand, shows a 10% lower fuel consumption, which is close to the actual optimum, at the same cycle times, and is able to complete a much larger part of the evaluation cycles.Re´sume´-De´veloppement de concepts d'une commande pre´dictive, destine´e a`une application pour chargeur sur pneus -Ce document pre´sente deux me´thodes de conception, base´es sur la programmation dynamique, pour la commande a`un pas de pre´diction d'une transmission continuˆment variable (Continuously Variable Transmission, CVT) d'un chargeur sur pneus. La premie`re me´thode de´veloppe´e, appele´e programmation dynamique stochastique (Stochastic Dynamic Programming, SDP) utilise une pre´diction statistique de la charge et la programmation dynamique stochastique pour minimiser l'utilisation de carburant. La seconde me´thode de´veloppe´e, appele´e programmation dynamique a`temps libre (Free-Time Dynamic Programming, FTDP), e´tablit la vitesse du ve´hicule en tant qu'e´tat et introduit un retard de 0,1 s dans les commandes du godet pour minimiser a`la fois l'utilisation de carburant et le temps ne´cessaire a`l'ope´ration. Les me´thodes sont e´value´es en s'appuyant sur 34 cycles de chargement mesure´s, utilise´s selon la me´thode de validation croise´e « leave-one-out ». L'e´valuation montre que la me´thode SDP requiert environ 1 dixie`me de l'effort de calcul de la me´thode FTDP, et qu'elle a un impact plus transparent sur les e´carts dans la pre´diction du cycle. D'un autre coˆte´, avec la me´thode FTDP on obtient une re´duction de 10 % de la consommation de carburant, ce qui est proche de l'optimum re´el, pour les meˆmes dure´es de cycle, et elle permet de re´aliser une plus grande partie des cycles d'e´valuation.

Achievement of Fuel Savings in Wheel Loader by Applying Hydrodynamic Mechanical Power Split Transmissions

“…Moreover, both the lateral dynamics of vehicle and wheel slippage are ignored in this derivation, since this study focuses on the longitudinal dynamics of the vehicle. Similar assumptions can be found in [3,19]. Figure 4a-d present the typical operating mode of this wheel loader.…”

“…To evaluate the performance of a wheel loader such as the working time cost, loading material volume and fuel consumption, a definite operating mode is required to describe the power requirements for the typical working manner of the wheel loader [3,13]. The most common working manner for a wheel loader is the V-type route that consists of five segments [15,16].…”

“…However, the HMPST is a self-adaptive mechanism and thus it cannot actively control the engine to work in a specified areas. On the other hand, the wheel loader operation is highly repetitive, that means the general operating mode of wheel loaders can be predicted and modeled [3,13]. Considering these two aspects, this paper optimizes HMPSTs using some features of the typical operating mode, in order to find the optimal fuel saving potential solution for HMPSTs.…”

“…However, owing to the double energy conversion in the TC and high slip between two terminals that performance inevitably, results in high losses. The low efficiency of the TC is the main reason for the excessive fuel losses of wheel loaders [3]. With the increasing emphasis on fuel savings and emission reduction worldwide, The hydrodynamic mechanical power split transmission (HMPST) can be a desirable choice, since in it a part of the power is transferred by the mechanical branch and the rest is transferred through the TC [5,6].…”

Optimal Predictive Control of Wheel Loader Transmissions

“…Basic descriptions and models of torque converters can be found in [27] and in [25], and in papers where the devices are used, such as in [37], [62] and [69]. The characteristics of a torque converter generally follows, and is usually presented as in, the example in Figure 1.2.…”