Smooth turning path generation for agricultural vehicles in headlands

Theoretical Investigations of the Headland Turning Agility of a Trailed Asymmetric Implement-and-Tractor Aggregate

“…This extra period of time is affected by: (i) the design of the entire machine-and-tractor aggregate; (ii) the steering peculiarities of the aggregating tractor; (iii) the personal qualities of the tractor driver, and so on. Furthermore, during this time the trajectory of the aggregating tractor is a clothoid, which allows a smooth transition from zero curvature to the curvature corresponding to radius R amin [14]. As is already known, the curvature is the reciprocal of the turning radius.…”

“…Finally, another important parameter of any implement-and-tractor aggregate is the lowest headland width E min for the turning manoeuvre. As known, different continuous-curvature paths are used in headlands, adjusted to the farmer's requirements [14]. The movement of the harvesting implement-and-tractor aggregates on the turning strip usually consists of a combination of two kinds of turns: a "pear-shaped loop-turn" and a "U-turn" with a straight strip (Figure 4) [9].…”

“…Incorrectly executed turns increase the width of the turning strips, significantly enlarging the idle path of the implement-and-tractor aggregate, with a negative effect on its efficiency [13]. The ability of an implement-and-tractor aggregate to perform manoeuvres along paths of a certain curvature can be considered as its turning agility, that is to say that the greater the curvature of the indicated path (or the smaller its radius of curvature), the higher the turning agility of the implement-and-tractor aggregate [14].The car theory developed at the present time distinguishes three cases concerning turning agility: neutral turning agility occurs if the curvature of the path does not depend on the car speed, excessive turning agility occurs if the curvature of the path increases with the car speed and insufficient turning agility occurs if the curvature of the path decreases with the car speed increasing [15,16].Obviously, in the theory of the turning agility concerning a car, its forward speed plays a dominant role, as it is usually quite high. Conversely, in the theory of the turning agility regarding the agricultural implement-and-tractor units, speed of motion also plays an important role, but is less dominant than in the theory of the car steering [17].…”

“…Incorrectly executed turns increase the width of the turning strips, significantly enlarging the idle path of the implement-and-tractor aggregate, with a negative effect on its efficiency [13]. The ability of an implement-and-tractor aggregate to perform manoeuvres along paths of a certain curvature can be considered as its turning agility, that is to say that the greater the curvature of the indicated path (or the smaller its radius of curvature), the higher the turning agility of the implement-and-tractor aggregate [14].…”

Research on the path optimization of unmanned rolling impaction for high embankment of airport

“…Bayar et al (2016) has employed the fourth-order polynomial to generate the agricultural machinery steering path. Backman et al (2015) proposed an algorithm with continuous curvature and velocity to solve the problem of smooth steering of agricultural vehicles. In the automatic parking system, there are also related studies on the curvature continuity problem.…”