minsnappolytraj

Generate minimum snap trajectory through waypoints

Since R2021b

Syntax

[q,qd,qdd,qddd,qdddd,pp,tPoints,tSamples] = minsnappolytraj(waypoints,timePoints,numSamples)

[q,qd,qdd,qddd,qdddd,pp,tPoints,tSamples] = minsnappolytraj(___,Name=Value)

[q,qd,qdd,qddd,qdddd,pp,tPoints,tSamples] = minsnappolytraj(___,TimeAllocation=true)

Description

[q,qd,qdd,qddd,qdddd,pp,tPoints,tSamples] = minsnappolytraj(waypoints,timePoints,numSamples) generates a minimum snap polynomial trajectory that achieves a given set of input waypoints with their corresponding time points. The function returns positions, velocities, accelerations, jerks, and snaps at the given number of samples numSamples. The function also returns the piecewise polynomial pp form of the polynomial trajectory with respect to time, as well as the time points tPoints, and the sample times tSamples.

[q,qd,qdd,qddd,qdddd,pp,tPoints,tSamples] = minsnappolytraj(___,Name=Value) specifies options using one or more name-value pair arguments in addition to the input arguments from the previous syntax. For example, minsnappolytraj(waypoints,timePoints,numSamples,VelocityBoundaryCondition=[1 0 -1 -1; 1 1 1 -1]) generates a two-dimensional minimum snap trajectory and specifies the velocity boundary conditions in each dimension for each waypoint.

[q,qd,qdd,qddd,qdddd,pp,tPoints,tSamples] = minsnappolytraj(___,TimeAllocation=true) optimizes a combination of snap and the total segment time cost. In this case, the function treats timePoints as an initial guess for the time of arrival at the waypoints.

Examples

Compute Minimum Snap Trajectory for 2-D Planar Motion

Use the minsnappolytraj function with a given set of 2-D xy waypoints. Time points for the waypoints are also given.

wpts = [1 4 4 3 -2 0; 0 1 2 4 3 1];
tpts = 0:5;

Specify the number of samples in the output trajectory.

numsamples = 100;

Compute minimum snap trajectories. The function outputs the trajectory positions (q), velocity (qd), acceleration (qdd), jerks (qddd), and snaps (qdddd) at the given number of samples.

[q,qd,qdd,qddd,qdddd,pp,timepoints,tsamples] = minsnappolytraj(wpts,tpts,numsamples);

Plot the trajectories for the x- and y-positions. Compare the trajectory with each waypoint.

plot(tsamples,q)
hold on
plot(timepoints,wpts,'x')
xlabel('t')
ylabel('Positions')
legend('X-positions','Y-positions')
hold off

You can also verify the actual positions in the 2-D plane. Plot the separate rows of the q vector and the waypoints as x- and y- positions.

figure
plot(q(1,:),q(2,:),'.b',wpts(1,:),wpts(2,:),'or')
xlabel('X')
ylabel('Y')

Input Arguments

waypoints — Waypoints for trajectory

n-by-p matrix

Waypoints for the trajectory, specified as an n-by-p matrix. n is the dimension of the trajectory, and p is the number of waypoints.

Example: [2 5 8 4; 3 4 10 12]

Data Types: single | double

timePoints — Time points for waypoints of trajectory

p-element row vector

Time points for the waypoints of the trajectory, specified as a p-element row vector. p is the number of waypoints.

Example: [1 2 3 5]

Data Types: single | double

numSamples — Number of samples in output trajectory

positive integer

Number of samples in the output trajectory, specified as a positive integer.

Example: 50

Data Types: single | double

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: minsnappolytraj(waypoints,timePoints,numSamples,VelocityBoundaryCondition=[1 0 -1 -1; 1 1 1 -1]) generates a two-dimensional minimum snap trajectory and specifies the velocity boundary conditions in each dimension for each waypoint.

VelocityBoundaryCondition — Velocity boundary conditions for each waypoint

n-by-p matrix

Velocity boundary conditions for each waypoint, specified as an n-by-p matrix. Each row sets the velocity boundary for the corresponding dimension of the trajectory at each of p waypoints. By default, the function uses a value of 0 at the boundary waypoints and NaN at the intermediate waypoints.

Example: VelocityBoundaryCondition=[1 0 -1 -1; 1 1 1 -1]

Data Types: single | double

AccelerationBoundaryCondition — Acceleration boundary conditions for each waypoint

n-by-p matrix

Acceleration boundary conditions for each waypoint, specified as an n-by-p matrix. Each row sets the acceleration boundary for the corresponding dimension of the trajectory at each of p waypoints. By default, the function uses a value of 0 at the boundary waypoints and NaN at the intermediate waypoints.

Example: AccelerationBoundaryCondition=[1 0 -1 -1; 1 1 1 -1]

Data Types: single | double

JerkBoundaryCondition — Jerk boundary conditions for each waypoint

n-by-p matrix

Jerk boundary conditions for each waypoint, specified as an n-by-p matrix. Each row sets the jerk boundary for the corresponding dimension of the trajectory at each of p waypoints. By default, the function uses a value of 0 at the boundary waypoints and NaN at the intermediate waypoints.

Example: JerkBoundaryCondition=[1 0 -1 -1; 1 1 1 -1]

Data Types: single | double

SnapBoundaryCondition — Snap boundary conditions for each waypoint

n-by-p matrix

Snap boundary conditions for each waypoint, specified as an n-by-p matrix. Each row sets the snap boundary for the corresponding dimension of the trajectory at each of p waypoints. By default, the function uses a value of 0 at the boundary waypoints and NaN at the intermediate waypoints.

Example: SnapBoundaryCondition=[1 0 -1 -1; 1 1 1 -1]

Data Types: single | double

TimeAllocation — Time allocation flag

false or 0 (default) | true or 1

Time allocation flag, specified as a logical 0 (false) or 1 (true). Enable this flag to optimize a combination of snap and total segment time cost.

Note

If singularity occurs when the time allocation flag is enabled, reduce the MaxSegmentTime to MinSegmentTime ratio.

Example: TimeAllocation=true

Data Types: logical

TimeWeight — Weight for time allocation

100 (default) | positive scalar

Weight for time allocation, specified as a positive scalar.

Example: TimeWeight=120

Data Types: single | double

MinSegmentTime — Minimum time segment length

0.1 (default) | positive scalar | (p–1)-element row vector

Minimum time segment length, specified as a positive scalar or (p–1)-element row vector.

Example: MinSegmentTime=0.2

Data Types: single | double

MaxSegmentTime — Maximum time segment length

1 (default) | positive scalar | (p–1)-element row vector

Maximum time segment length, specified as a positive scalar or (p–1)-element row vector

Example: MaxSegmentTime=5

Data Types: single | double

Output Arguments

q — Positions of trajectory

n-by-m matrix

Positions of the trajectory at the given time samples in tSamples, returned as an n-by-m matrix. n is the dimension of the trajectory, and m is equal to numSamples.

qd — Velocities of trajectory

n-by-m matrix

Velocities of the trajectory at the given time samples in tSamples, returned as an n-by-m matrix. n is the dimension of the trajectory, and m is equal to numSamples.

qdd — Accelerations of trajectory

n-by-m matrix

Accelerations of the trajectory at the given time samples in tSamples, returned as an n-by-m matrix. n is the dimension of the trajectory, and m is equal to numSamples.

qddd — Jerks of trajectory

n-by-m matrix

Jerks of the trajectory at the given time samples in tSamples, returned as an n-by-m matrix. n is the dimension of the trajectory, and m is equal to numSamples.

qdddd — Snaps of trajectory

n-by-m matrix

Snaps of the trajectory at the given time samples in tSamples, returned as an n-by-m matrix. n is the dimension of the trajectory, and m is equal to numSamples.

pp — Piecewise polynomial

structure

Piecewise-polynomial, returned as a structure that defines the polynomial for each section of the piecewise trajectory. You can build your own piecewise polynomials using mkpp, or evaluate the polynomial at specified times using ppval. The structure contains the fields:

• form: 'pp'.

• breaks: p-element vector of times when the piecewise trajectory changes forms. p is the number of waypoints.

• coefs: n(p–1)-by-order matrix for the coefficients for the polynomials. n(p–1) is the dimension of the trajectory times the number of pieces. Each set of n rows defines the coefficients for the polynomial that described each variable trajectory.

• pieces: p–1. The number of breaks minus 1.

• order: Degree of the polynomial + 1. The order of polynomial is 10.

• dim: n. The dimension of the control point positions.

tPoints — Time points for waypoints of trajectory

p-element row vector

Time points for the waypoints of the trajectory, returned as a p-element row vector. p is the number of waypoints.

tSamples — Time samples for trajectory

m-element row vector

Time samples for the trajectory, returned as an m-element row vector. Each element of the output position q, velocity qd, acceleration qdd, jerk qddd, and snap qdddd has been sampled at the corresponding time in this vector.

References

[1] Bry, Adam, Charles Richter, Abraham Bachrach, and Nicholas Roy. “Aggressive Flight of Fixed-Wing and Quadrotor Aircraft in Dense Indoor Environments.” The International Journal of Robotics Research, 34, no. 7 (June 2015): 969–1002.

[2] Richter, Charles, Adam Bry, and Nicholas Roy. “Polynomial Trajectory Planning for Aggressive Quadrotor Flight in Dense Indoor Environments." Paper presented at the International Symposium of Robotics Research (ISRR 2013), 2013.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2021b