Adaptive control of a farm tractor with varying yaw dynamics accounting for actuator dynamics and saturations

Adaptive steering control of a farm tractor with varying yaw rate properties

“…The tractor was outfitted with a StarFire DGPS receiver with 10-cm circular error probable (CEP) accuracy. For a more in-depth discussion of the experimental setup, see Derrick (2008). Two different types of experiments are presented: step input tests and steady-state lateral position tests.…”

A Low-Cost Platform for Modeling and Controlling the Yaw Dynamics of an Agricultural Tractor to Gain Autonomy

“…x is the compact state vector; ω z . δ dact R is the angular velocity of turn (rad/s), which is in synchrony with δ d [34,35], considering ω z 0, with ω zmin ≤ |ω z | > 0, with a minimum value of (ω zmin ), for a time t ≥ 0 s when the sensor SR-PS100 does not detect δ d , and R > 0 is a constant gain which is chosen so that the angular velocity of the turn is not saturated, which relates the input voltage on the actuator with the angular velocity which is obtained from [36]; α f , α r are front and rear side slip angles (rad); δ d , δ c are the tire angle components imposed by the driver and controller (rad); imposed on the front tires ( = + ), where and are the angles imposed on the front tire of the driver and controller, respectively; and the lateral slip angles of the tires are defined as follows:…”

“…The mathematical model for a farm vehicle can be established as a rigid body moving in free space of two or three degrees of freedom connected to a flat land surface through the tires (Figure 3). Besides, when considering the estimation of linear and nonlinear dynamics, these can be analyzed in a simplified way with the so-called bicycle model [32,33], resulting in being able to propose a measurement of the variable : ≅̇ is the angular velocity of turn (rad/s), which is in synchrony with [34,35], considering ≠ 0, with ≤ | | > 0, with a minimum value of ( ), for a time t≥ 0 when the sensor SR-PS100 does not detect , and R > 0 is a constant gain which is chosen so that the angular velocity of the turn is not saturated, which relates the input voltage on the actuator with the angular velocity which is obtained from [36]; , are front and rear side slip angles (rad); , are the tire angle components imposed by the driver and controller (rad); ̇= ( − )/ is the angular velocity response of the actuator on the tractor steering wheel (rad/s) and is established as +DDELTAD 1 VOL and +DDELTAD 2 VOL on the PPTD shown in Appendix A, where is the input voltage to actuator (V), > 0 is an estimated back electromotive force constant (V/(rad/s)), is the resistance of the actuator (Ω ), and is the current (A), considering the simplified mathematical model of the cc motor where its values are obtained experimentally; the moment of turn resulting from the active brakes (N m); lateral forces , , , (N) are functions of the angle…”

A Simplified Optimal Path Following Controller for an Agricultural Skid-Steering Robot

“…The simplest methods are related to the geometry of the vehicle and some examples are Follow the Carrot [22], Pure Pursuit [23] and Stanley method, being the latest one of the most widely used and its name comes from the robot that won the 2005 DARPA Grand Challenge [24]. For kinematic and dynamic models, the complexity increases and one way to deal with this, is to separate the yaw rate control and the tracking control to deal with them separately and apply adaptive control to approximate the yaw rate dynamics as presented in [25]- [29]. Nevertheless, none of these methods have been applied to a skid-steering robot.…”