propagateWhileValid

Propagate system and return valid motion

Since R2021b

Syntax

[q,u,steps] = propagateWhileValid(mobileProp,q0,u0,qTgt,maxSteps)

Description

[q,u,steps] = propagateWhileValid(mobileProp,q0,u0,qTgt,maxSteps) iteratively propagates the system from the current state q0 towards a target state qTgt with an initial control input u0 for a maximum number of steps maxSteps.

At the end of each propagation step i, the system returns these values:

• q(i,:) — Current state of the system

• u(i,:) — Control input for step i + 1

• steps(i) — Number of steps between i - 1 and i

The function validates all propagations and returns system information between q0 and the last valid state.

Examples

Propagate Mobile Robot

Load a ternary map matrix and create an occupancyMap object. Create the state propagator using the map.

load("exampleMaps","ternaryMap")
map = occupancyMap(ternaryMap,10);
propagator = mobileRobotPropagator(Environment=map);

Set the state bounds on the state space based on the map world limits.

propagator.StateSpace.StateBounds(1:2,:) = [map.XWorldLimits; 
                                            map.YWorldLimits];

Specify the start and goal states.

start = [10 15 0];
goal  = [40 30 0];

Specify the initial control and maximum number of steps.

u0 = [0.2 -0.2];
maxSteps = 2000;

Propagate the state of the robot without validation.

[q1,u1,steps1] = propagate(propagator,start,u0,goal,maxSteps);

Visualize the results.

figure
show(map)
hold on
plot(start(1),start(2),"rx")
plot(goal(1),goal(2),"go")
plot(q1(:,1),q1(:,2),"m")
hold off

Propagate the state of the robot and return valid motion.

[q2,u2,steps2] = propagateWhileValid(propagator,start,u0,goal,maxSteps);

Visualize the results.

figure
show(map)
hold on
plot(start(1),start(2),"rx")
plot(goal(1),goal(2),"go")
plot(q2(:,1),q2(:,2),"m")
hold off

Input Arguments

mobileProp — Mobile robot state propagator

mobileRobotPropagator object

Mobile robot state propagator, specified as a mobileRobotPropagator object.

q0 — Initial state

s-element vector

Initial state of the system, specified as an s-element vector. s is the number of state variables in the state space.

u0 — Initial control on initial state

c-element vector

Initial control on the initial state, specified as an c-element vector. c is the number of control inputs.

qTgt — Target state

s-element vector

Target state of the system, specified as an s-element vector. s is the number of state variables in the state space.

maxSteps — Maximum number of steps

positive scalar

Maximum number of steps, specified as a positive scalar.

Output Arguments

q — Propagated states

n-by-s matrix

Propagated states of the system, returned as an s-element vector. s is the number of state variables in the state space.

u — Control inputs for propagating states

n-by-c matrix

Control inputs for propagating states, returned as an n-by-c matrix. c is the number of control inputs

steps — Number of steps from each state and control input to next

n-element vector of positive integers

Number of steps from each state and control input to next, returned as an n-element vector of positive integers.

Version History

Introduced in R2021b