def __init__(self, params, env_map):
self.world_params = params['world']
self.robot_params = params['robot']
self.sensor_params = params['sensor']
self.num_particles = params['sim']['num_particles']
self.goal_pos = params['sim']['goal_pos']
self.goal_radius = params['sim']['goal_radius']
self.map_belief = env_map
self.state_belief = np.zeros(2)
# Belief map
self.timestep = 0
self.w_slow = None
self.w_fast = None
l,w = self.map_belief.shape
# Discretized Actions
self.actions = [{'dturn':dt, 'dmove':dm} for dt in [-np.pi/4, 0, np.pi/4] for dm in [2,-2]]
# Value map from value iteration algorithm
trans_sim = lambda state, act : calc_move(self.robot_params, state, act, self.map_belief)
self.vi = ValueIteration(env_map, trans_sim, self.actions, self.reward)
self.vi.solve()
# Particle filter
# Each row represents one particle of (pos_x, pos_y, orient)
self.particles = self.gen_rand_particles(self.num_particles)
def pred_step(self, action):
# Update Particles in prediction step
tmp = np.zeros(self.particles.shape)
for i in np.arange(self.num_particles):
state = self.particles[i,:]
tmp[i,:] = calc_move(self.robot_params, state, action, self.map_belief)
self.particles = tmp
def get_action(self, readings):
# Find ML estimate of position from particles
# discretize action set
act_vals = np.zeros((self.num_particles, len(self.actions)));
for i in range(self.num_particles):
for j in range(len(self.actions)):
state = self.particles[i,:]
action = self.actions[j]
[nsx,nsy,nso] = calc_move(self.robot_params, state, action, self.map_belief)
# lookup value at new state
act_vals[i,j] = self.vi.get_val((nsx,nsy,nso))
# Take greedy action with the highest expected value
sum_vals = np.sum(act_vals,axis=0)
max_ind = np.argmax(sum_vals)
return self.actions[max_ind]