#include <stop.h>
Public Member Functions | |
| result_t | control (pilot_command_t &pcmd, float distance, float threshold, float topspeed=3.0) |
| result_t | control (pilot_command_t &pcmd) |
| void | reset (void) |
| Stop (Navigator *navptr, int _verbose) | |
| ~Stop () | |
Private Attributes | |
| bool | creeping |
| double | initial_speed |
| bool | stopping |
Definition at line 14 of file stop.h.
| Stop::Stop | ( | Navigator * | navptr, | |
| int | _verbose | |||
| ) |
This is based on the unpublished "Control Tutorial" draft dated January 26, 2004 by Dr. Benjamin Kuypers, section 5: "The Stopping Controller". He recommends a constant deceleration instead of the simpler exponential decay. The dynamical system is:
x_dot = -k * sqrt(x)
Solving analytically with initial condition x(0) = D and v(0) = V yields these equations of motion:
x(t) = (sqrt(D) - V*t/(2*sqrt(D)))**2 (parabolic drop) v(t) = dx/dt = (V**2/2*D)*t + V (linear velocity) a(t) = dv/dt = V**2/(2*D) = A (constant deceleration)
Note that the initial velocity V is negative in these equations, because it represents motion from positive x to zero. The system stops in finite time T = -2*D/V, with x(T) = 0, and v(T) = 0.
For example, when D = 10m from stop line and V = -5m/s, the vehicle stops in 4 seconds at a constant 1.25m/s/s deceleration.
| Controller::result_t Stop::control | ( | pilot_command_t & | pcmd, | |
| float | distance, | |||
| float | threshold, | |||
| float | topspeed = 3.0 | |||
| ) |
Set speed for steady deceleration for stop distance
| pcmd | contains desired heading and speed, assuming it is not yet time to stop, updated on exit | |
| distance | to stop location along current path | |
| threshold | close enough distance | |
| topspeed | velocity limit |
| Controller::result_t Stop::control | ( | pilot_command_t & | pcmd | ) | [virtual] |
Reimplemented from Controller.
| void Stop::reset | ( | void | ) | [virtual] |
Reimplemented from Controller.
bool Stop::creeping [private] |
double Stop::initial_speed [private] |
bool Stop::stopping [private] |
