  We present a trajectory generation framework for control of wheeled vehicles
under steering actuator constraints. The motivation is smooth autonomous
driving of heavy vehicles. The key idea is to take into account rate, and
additionally, torque limitations of the steering actuator directly. Previous
methods only take into account curvature rate limitations, which deal
indirectly with steering rate limitations. We propose the new concept of
Sharpness Continuous curves, which uses cubic and sigmoid curvature
trajectories together with circular arcs to steer the vehicle. The obtained
trajectories are characterized by a smooth and continuously differentiable
steering angle profile. These trajectories provide low-level controllers with
reference signals which are easier to track, resulting in improved performance.
The smoothness of the obtained steering profiles also results in increased
passenger comfort. The method is characterized by a fast computation time,
which can be further speeded up through the use of simple pre-computations. We
detail possible path planning applications of the method, and conduct
simulations that show its advantages and real time capabilities.
