Planning: (1) fixed smooth issue by adjusting parameters. (2) Increased planning robustness with sacrificing the initial continuity of acceleration.
(2) comes from an intrinsic issue when we use spline curves to fit all planning results ---- NOT all cases can be fitted by spline!
We should evaluate the necessity of using splines, especially when the
cost is that planning might fail in some cases. In the future version, we should not focus only
on the smoothness of the curves. Perfect smoothness can only live in an unrealistic imaginary world.
We should also notice that the smoothness of planning results doesn't
exactly correlate to what people feel when sitting on a car.