CAJ | 학술논문

针对路感特性是线控转向技术的难点之一，设计与评价了轮式拖拉机线控液压转向系统的路感特性。分析了路感的评价指标、产生机理及拖拉机等农用车辆行车环境差异大的特殊性；实测了拖拉机在旱地、土路、水泥路、沥青路等路面上的原地转向与行驶时的转向阻力，以指导设计模式化路感特性与模式识别系统。农田作业模式侧重于路感的轻便性，驾驶员作用在方向盘上的切向力为2～10.127 N，车速低于11 km/h；非农田作业模式侧重于路感的真实度，切向力范围为2.5～52.5 N，车速低于30 km/h。完成了路感的主观评价，评价结果表明模式化路感特性可以令驾驶员满意。设计的模式化路感可以有效改善拖拉机的驾驶感觉，推动线控液压转向系统的发展。
침대로감특성시선공전향기술적난점지일，설계여평개료륜식타랍궤선공액압전향계통적로감특성。분석료로감적평개지표、산생궤리급타랍궤등농용차량행차배경차이대적특수성；실측료타랍궤재한지、토로、수니로、력청로등로면상적원지전향여행사시적전향조력，이지도설계모식화로감특성여모식식별계통。농전작업모식측중우로감적경편성，가사원작용재방향반상적절향력위2～10.127 N，차속저우11 km/h；비농전작업모식측중우로감적진실도，절향력범위위2.5～52.5 N，차속저우30 km/h。완성료로감적주관평개，평개결과표명모식화로감특성가이령가사원만의。설계적모식화로감가이유효개선타랍궤적가사감각，추동선공액압전향계통적발전。
The hydraulic steer-by-wire system has no mechanical connection between the handwheel and front steering wheel. In other words, the road-feeling has no direct force contact with the tires, and it can be designed freely or by driver's preference. The design of road-feeling is one of the most difficult problems for steer-by-wire technology. Most drivers prefer lighter road-feeling, but at the same time, too light road-feeling can’t help driver to supervise the vehicle operation and judge the condition of road face. So it’s worthy to study the road-feeling characteristics. The paper chose the wheeled tractor as the study objective. In order to finish the study better and design road-feeling characteristic more reasonably, the paper first analyzed the evaluation index with the help of abundant references. Then the generating mechanism of road-feeling for tractors was relearned, because wheeled tractor not only works in the field but also travels on the road, and the driving environment of tractors has the large difference compared with other farm vehicles. When tractor works in the field with low speed and without pedestrian and other vehicles, the driver doesn’t need to pay much attention to safety and prefers lighter road-feeling, but when tractor travels on the road from one place to another, such as dry land, dirt road, cement road and asphalt pavement, the speed is higher, nearly reaching up to 30 km/h, and with many pedestrians and vehicles around, so the driver needs to supervise the vehicle operation carefully and judge the information of road rightly with the help of high road-feeling. The paper measured the steering resistance of JS-754 tractor on the above 4 kinds of roads to guide the design of road-feeling characteristic. The modeled road-feeling was designed based on tractor speed and steering resistance by taking the driving environment difference into account, including cropland working mode and non-cropland traveling mode. The road-feeling value was calculated by tractor speed and steering resistance. The cropland working mode mainly was targeted to reduce the driver’s work intensity. The tangential force that drivers exerted on the handwheel was 2-10.127 N in cropland working mode with the speed below 11 km/h. At the same time, the non-cropland traveling mode mainly focused on safety, supplying more distinct road-feeling to help driver to supervise vehicle operation accurately and do right operation. The tangential force that drivers needed to exert on the handwheel was 2.5-52.5 N, and the vehicle speed was lower than 30 km/h according to government standard under non-cropland traveling mode. In addition, the identification system was designed to fit the modeled road-feeling, including manual and automatic identification. The driver could choose identified way by three-position switch, and the controller determined the road-feeling mode and road-feeling value according to current speed, steering resistance and drivers’ choice. Furthermore, the non-cropland mode was defined as safe mode and must be applied when speed was higher than 11 km/h. At last, the paper finished the objective evaluation about the designed road-feeling characteristic with the help of the developed experiment platform, and the steering resistance loading system was designed for the test. Ten experienced tractor drivers attended the questionnaire survey after they finished driving the experiment platform with the designed road-feeling. Drivers felt the speed just by value displayed on monitor instead of dynamic feeling. During the test, the linear, step, and sinusoidal steering resistances were loaded to simulate the physical truth. The results showed that the objective evaluation score was reasonable, which meant the designed modeled road-feeling could be used in all wheeled tractors and satisfy most drivers’ preference. In summary, the designed road-feeling can make driving feeling better and promote the development of hydraulic steering by wire.