# Questions tagged [trajectory]

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### Trajectory waypoints are not exactly the same as joint positions. How to find the closest waypoint?

I'm trying to implement a function to pause the execution of a trajectory, and then re-plan a trajectory following the remaining path. The framework I'm using is moveit noetic. ...
32 views

### Save robot trajectory as a single figure/image

I would like to show the path planned by moveit2 as a figure in a paper I'm writing. I've seen figures with multiple semi-transparent manipulator arms showing various stages of a certain trajectory, (...
21 views

### Path and trajectory planning for a holonomic drivetrain with non zero starting velocities

What path planning algorithms are typically used for holonomic drivetrains that can avoid collisions while also starting with non zero velocities. I am working on a project where I am planning to have ...
1 vote
112 views

### How do I calculate reference trajectory for a robot following a parabolic path at a constant speed?

I have a 3 DOF robot arm and have been tasked with making it follow a path of $y=6-x^2$. Normally to compute the reference trajectory, I would simply create a linearly spaced vector of $x$ values and ...
1 vote
20 views

### How to avoid Cusps and Corners when generating spline?

Here I wrote Qubic spline trajectory generation. The following are the result. Spline that generated Curvature of the spline Yaw angle changes According to Figure 02, there is a sharp change in yaw ...
19 views

### Smooth a timestamped series of translation and quaternion samples

I have a rosbag of transforms (of type TransformStamped) I'd like to smooth a small amount without altering the overall trajectory much, just reduce the higher ...
132 views

### Trajectory generation for robotic manipulator using trapezoidal velocity profile in MATLAB

I am trying to write code in MATLAB to generate a trajectory for a scara manipulator in the robot operational space with trapezoidal velocity profile for each segment passing through 5 waypoints using ...
491 views

### Designing S-Curve velocity profile for given Distance

I'm trying to create a high-level API for controlling a drone, where I tell it how far I want it to go (eg. moveForward(10)). The SDK allows me to give the drone an ...
94 views

### how the two equatoin are linearized

corresponding paper Question1: how the equatoin 3 is linearized in the neighborhood of the equilibrium point $x = x_{sp}, \dot x =0$ Question2: how the equatoin 12 is linearized in the neighborhood ...
35 views

I have defined a quadcopter that I control with a PID controller. The dynamics that define it are such. $T=mg+m\ddot{z}$ $\theta=\frac{\ddot{x}}{-9.82}$ $\phi=\frac{\ddot{y}}{9.82}$ As you can see I ...
139 views

### Joint space trajectory script unclear

I have a script provided by The MathWorks Inc. that makes a robot end-effector follow both a task space and a joint space trajectory through several waypoints. These trajectories are then plotted in ...
36 views

### Decidability of Pursuit-Evasion games and self driving cars

I was wondering if there is any theory describing the decidability of a continuous pursuit-evasion game with constraints. Scenario: Two cars approach each other on a street with two lanes. Let's say ...
1 vote
67 views

### Why is a joint space trajectory unable to deal with operational space obstacles?

I have found several sources that state that a Joint space trajectory model is not capable of dealing with obstacles in the manipulator workspace. These sources include: slide 10 of "Manipulator ...
25 views

### Matlab smooth transition between stored configurations (rigid body tree robot )

I currently have a few joint configurations stored for a robot model in Matlab. When I play back and show the robot in different configurations, there is of course no smooth, but abrupt transition. Is ...
39 views

### Is there any need to guarantee the duration of one planned trajectory is an integer times rather than a decimal times of interpolation period Ti

Take double S of velocity profile for example where the seven segments exist. Given the desired displacement s, the constraints ...
165 views

### How to design a PID controller for boat?

I have a boat with two trusters and a trajectory planner which is based on the bicycle model. In order to control the boat, the linear velocity of each truster has to be provided. The following ...
137 views

### Relative scale problem

I am doing Monocular Visual Odometry, and I have problem with relative scale. Most of the time its value is between 0.8-1.1, but sometimes it goes crazy and it has value 3,4 and once it had value 25. ...
101 views

### How to investigate the relation between planning frequency and control response?

I have a speed control system which is part of a hierarchical planning and control stack. The final output of this system is torque and the input is desired speed. The system is experiencing some ...
1 vote
41 views

I'm currently following a course on coursera on quadrotors, and i'm currently focusing on the trajectory planning mechanism. In the course, it's said that one of the criterias when planning a ...
223 views

### Trajectory generation equation from jacobian and inverse kinematics

I just built a 4 DOF Articulated manipulator with open-loop servo motors and the servos signals are generated using a micro-controller. I followed the Angela Sodemann's videos on YouTube, I calculated ...
1 vote
40 views

### How to estimate gradient of Jerk

A trajectory is described by a position vector, i.e., traj = $[q_0, q_1,...,q_n]$. The objective is to minimize the jerk of the trajectory. I am referring to this code to understand how the gradient ...
249 views

### Generate a Trajectory from GPS coordinates

How would I generate a trajectory (e.g. minimum snap/jerk/acceleration) for a quad rotor between GPS coordinates? In all the examples that I have seen, they assume that the x,y positions are in meters ...
1 vote
25 views

### Can I relate trajectory generation to differential inverse kinematics?

I am wondering how (if) one can translate trajectories of translation matrices to joint velocities? I'm reading the notes of Russ Tedrake's class on manipulation. One part of the notes concerns a ...
66 views

### Sinusoidal trajectory of each cartesian coordinate for the end effector

Consider a 7-DOF robotic manipulator. I want the end effector to follow a predefined trajectory and suppose I care only about the position and not about the orientation. So, the rotation part of the ...
92 views

### Problem designing acceleration inputs controller

I am reading this paper: https://www.researchgate.net/publication/224635390_The_motion_control_problem_for_the_CyberCarpet in which is implemented a cartesian regulator to bring the position $(x,y)$ ...
497 views

### Motion profile and Motion control scheme, how do they interact?

I'm studying motion control and I start with the simplest case, I have to go from A to B in a straight line using a trapezoidal motion profile. I understand that in a real case, due to the fact that ...
83 views

### Trajectory planning in unstructured environments

How is trajectory planning normally carried out in off-road/unstructured environments? In particular I'm interested in how stereo vision can be used to plot trajectories over obstacles - for example, ...
1 vote
66 views

### My Pick and Place Program Not Working

hope you are all well. I am trying to finish a capstone project on Coursera. It asks me to carry a cube object from an initial position to goal. This video shows the movement. Project website: http://...
1 vote
238 views

### Compute orientation velocities 6-DOF robot

I am trying to compute the joint velocities a 6-DOF manipulator(a typical industrial robot). I have an initial position [xi, yi, zi, T1i, T2i, T3i] and goal position [xf, yf, zf, T1f, T2f, T3f] in the ...
987 views

### What is a cost and cost function in path planning?

Surfing through websites and videos, I interpreted that cost refers to parameters such as time taken to go from start position to the goal position or distance traveled in every possible path and cost ...
701 views

### SLERP velocity and acceleration (3d Orientation interpolation)

Hey guys I am quite new to quaternions and I am a bit unsure as to how to use them. How are the velocities and accelerations trajectories determined using quaternions? I have been using slerp to ...
51 views

### how do I decide what is the order of the polynomial I need to use in a polynomial iterpolation for a trajectory?

I am a student studying robotics, and I am focusing on trajectory planning for a robotic arm. In particular, I am studying polynomial interpolation for defining the trajectories, and I am having some ...
1 vote
90 views

### How do I find the minimum time for computing a trajecotry for a robotic arm?

I am studying robotics and I am focusing on trajectory planning. I have been struggling with this topic for a while, and I still have some doubts that I cannot solve. One of them is the following: I ...
1 vote
107 views

### Reset coordinate system of robot while maintaining relationship to the previous

I am currently estimating a robot's pose (3d position and rotation matrix) with an IMU and I want to reset the localizer in the middle of the run while keeping the relationship to the pose it had when ...
129 views

### where can I find a good source to study robotics kinematics and trajectory planning relative to robotic arm manipulator?

I am a student, and I have to study for a Robotics exam which consistes mainly in kinematics for a robotic manipulator and trajectory planning also for a robotic manipulator. In the part relative to ...
283 views

### Going from Spline to Differential Drive Command

I have a differential drive robot that needs to move along a path stored in its memory as a spline. I am currently trying to understand the mathematics of determining how much power to apply to each ...
350 views

### Why in trajectory planning in joint space the manipulator never crosses a singularity?

I am studying robotics kinematics and I have studied that if we plan a trajectory in joint space it is impossible for the robot manipulator to cross a singularity during its motion, while in cartesian ...
53 views

### Trajectory tolerance limits

I have a trajectory planner, which calculates the trajectory assuming that the robot is following the planned trajectory. From sensors I get the position of the robot, which has an offset from the ...
1 vote
2k views

### What are the differences between trajectory planning, trajectory tracking, path planning, path following and motion planning?

What are the differences between trajectory planning, trajectory tracking, path planning, path following and motion planning? And what are the basic methods they use?
1 vote
198 views

### Iterative calculation of trajectory

In the answer https://robotics.stackexchange.com/a/7512/22953 there is an example for trapetzoid trajectory planning that results in the following table. \begin{array} {|r|r|} \hline time &...
I have an initial position $X^R_{init}$ of the robot ($x$, $y$ and yaw) and a goal position $X^R_{goal}$ I need to create a trajectory of duration $T$ with $n$ waypoints to move the robot from its ...