Add function t2s to transform temporal state into spatial state.
Modify drive function to work in temporal domain. Add function get_current_waypoint to set the waypoint of the reference path based on the traveled distance s of the car.master
matssteinweg
parent
db90eb1055
commit
15fa9f5c33
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@ -2,6 +2,7 @@ import numpy as np
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from abc import ABC, abstractmethod
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import matplotlib.pyplot as plt
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import matplotlib.patches as plt_patches
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import math
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# Colors
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CAR = '#F1C40F'
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@ -25,6 +26,16 @@ class TemporalState:
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self.y = y
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self.psi = psi
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def __iadd__(self, other):
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"""
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Overload Sum-Add operator.
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:param other: numpy array to be added to state vector
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"""
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for state_id, state in enumerate(vars(self).values()):
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vars(self)[list(vars(self).keys())[state_id]] += other[state_id]
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return self
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########################
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# Spatial State Vector #
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@ -106,6 +117,9 @@ class SpatialBicycleModel(ABC):
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# Set initial distance traveled
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self.s = 0.0
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# Set sampling time to None (Initialization required)
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self.sampling_time = None
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# Set initial waypoint ID
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self.wp_id = 0
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@ -150,57 +164,57 @@ class SpatialBicycleModel(ABC):
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return x, y, psi
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def drive(self, input, state=None, kappa=None, delta_s=None):
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def t2s(self):
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"""
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Convert spatial state to temporal state. Either convert self.spatial_
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state with current waypoint as reference or provide reference waypoint
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and reference_state.
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:return x, y, psi
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"""
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# compute temporal state variables
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e_y = np.cos(self.current_waypoint.psi) * \
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(self.temporal_state.y - self.current_waypoint.y) - \
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np.sin(self.current_waypoint.psi) * (self.temporal_state.x -
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self.current_waypoint.x)
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e_psi = self.temporal_state.psi - self.current_waypoint.psi
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e_psi = np.mod(e_psi + math.pi, 2*math.pi) - math.pi
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t = 0
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return SimpleSpatialState(e_y, e_psi, t)
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def set_sampling_time(self, Ts):
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"""
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Set sampling time of bicycle model.
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:param Ts: sampling time in s
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"""
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self.Ts = Ts
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def drive(self, u):
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"""
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Drive.
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:param state: state vector for which to compute derivatives
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:param input: input vector
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:param kappa: curvature of corresponding waypoint
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:param u: input vector
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:return: numpy array with spatial derivatives for all state variables
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"""
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# Get spatial derivatives
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if state is None and kappa is None and delta_s is None:
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state = np.array(self.spatial_state[:])
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# Get delta_s | distance to next waypoint
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next_waypoint = self.reference_path.waypoints[self.wp_id + 1]
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delta_s = next_waypoint - self.current_waypoint
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# Get current curvature
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kappa = self.current_waypoint.kappa
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# Get input signals
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v, delta = u
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spatial_derivatives = self.get_spatial_derivatives(state, input, kappa)
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# Compute temporal state derivatives
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x_dot = v * np.cos(self.temporal_state.psi)
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y_dot = v * np.sin(self.temporal_state.psi)
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psi_dot = v / self.l * np.tan(delta)
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temporal_derivatives = np.array([x_dot, y_dot, psi_dot])
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# Update spatial state (Forward Euler Approximation)
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self.spatial_state += spatial_derivatives * delta_s
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# Update spatial state (Forward Euler Approximation)
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self.temporal_state += temporal_derivatives * self.Ts
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# Assert that unique projections of car pose onto path exists
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#assert self.spatial_state.e_y < (1 / (self.current_waypoint.kappa +
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# self.eps))
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# Compute velocity along path
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s_dot = 1 / (1 - self.spatial_state.e_y * self.current_waypoint.kappa) \
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* v * np.cos(self.spatial_state.e_psi)
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# Increase waypoint ID
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self.wp_id += 1
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# Update current waypoint
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self.current_waypoint = self.reference_path.waypoints[self.wp_id]
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# Update temporal_state to match spatial state
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self.temporal_state = self.s2t()
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# Update s | total driven distance along path
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self.s += delta_s
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# Linearize model around new operating point
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# self.A, self.B = self.linearize()
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else:
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spatial_derivatives = self.get_spatial_derivatives(state, input,
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kappa)
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# Update spatial state (Forward Euler Approximation)
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state += spatial_derivatives * delta_s
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return state
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# Update distance travelled along reference path
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self.s += s_dot * self.Ts
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def _compute_safety_margin(self):
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"""
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@ -213,6 +227,45 @@ class SpatialBicycleModel(ABC):
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return length, width
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def get_current_waypoint(self):
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"""
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Create waypoint on reference path at current location of car by
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interpolation information from given path waypoints.
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"""
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# Compute cumulative path length
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length_cum = np.cumsum(self.reference_path.segment_lengths)
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# Get first index with distance larger than distance traveled by car
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# so far
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greater_than_threshold = length_cum > self.s
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next_wp_id = greater_than_threshold.searchsorted(True)
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# Get previous index for interpolation
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prev_wp_id = next_wp_id - 1
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# Get distance traveled for both enclosing waypoints
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s_next = length_cum[next_wp_id]
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s_prev = length_cum[prev_wp_id]
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if np.abs(self.s - s_next) < np.abs(self.s - s_prev):
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self.wp_id = next_wp_id
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self.current_waypoint = self.reference_path.waypoints[next_wp_id]
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else:
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self.wp_id = prev_wp_id
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self.current_waypoint = self.reference_path.waypoints[prev_wp_id]
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#
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# # Weight for next waypoint
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# w = (s_next - self.s) / (s_next - s_prev)
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#
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# # Interpolate between the two waypoints
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# prev_wp = self.reference_path.waypoints[prev_wp_id]
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# next_wp = self.reference_path.waypoints[next_wp_id]
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# x = w * next_wp.x + (1 - w) * prev_wp.x
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# y = w * next_wp.y + (1 - w) * prev_wp.y
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# psi = w * next_wp.psi + (1 - w) * prev_wp.psi
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# kappa = w * next_wp.kappa + (1 - w) * prev_wp.kappa
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def show(self):
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"""
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Display car on current axis.
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