近代车辆转向梯形存在一个接近平行四边行的趋势。但在车辆大转角和低速转向情况下,这个几何特性可能导致回正力矩减小,甚至造成转向轮自行转至死点的现象。阿克曼(Ackerman)转向梯形理论认为,每一个前轮应该转至某一适当的角度,以使车轮转向运动完全符合它自然运动的轨迹。对于传统的四轮车辆,内前轮应转过一个较外前轮 Modern vehicle steering trapezoidal there is a parallel line near the trend. However, in the case of large-angle vehicle and low-speed steering, this geometric characteristic may result in a decrease of the back-to-back moment and may even cause the steering wheel to go to the dead point itself. Ackerman’s shift to trapezoidal theory argues that each front wheel should go to an appropriate angle so that the wheel’s steering motion exactly matches the trajectory of its natural motion. For conventional four-wheeled vehicles, the front front wheel should be rotated by an outer front wheel