27 votes
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What is the difference between path planning and motion planning?

Compare the following two images: The path planning is somewhat trivial. There's only one path: the rope. The motion planning on the other hand is not that easy. In a maze the path planning is hard ...
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7 votes
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Difference between kinematic, dynamic and differential constraints

Kinematic constraints involves only constraint on the motion (kinematics means the study of motion without considering the force that causes it), which may involve configuration variables and their ...
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  • 366
7 votes

Implementing a boustrophedon algorithm in a given room with obstacles

I implemented something like this in College: https://github.com/Auburn-Automow/au_automow_common/tree/master/automow_planning Basically we just passed the vertices of the boustrophedon path as ...
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  • 298
7 votes

Motion Planning vs. Control

There is a saying in software engineering which states that your company structure is reflected in your software architecture (I cannot recall the exact phrase). This is true for a robot control ...
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  • 6,437
6 votes
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rotation matrix to euler angles with gimbal lock

I think you may be misunderstanding the nature of gimbal lock. It sounds like you may be trying to remove an actual term in a rotation matrix calculation , but this is incorrect because each axis is ...
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  • 14.7k
6 votes

What is the difference between path planning and motion planning?

What's the difference between turn-by-turn GPS and driving a car? GPS is path planning: high-level commands like, "turn right in 1 mile." Driving is motion planning, which means following a route ...
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5 votes
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What are the advantages of optimal control as opposed to control theory?

Classical control theory requires Linear Time Invariant systems. Most robots of interest actually have non-linear dynamics. Of course many optimal control techniques also require linear systems. LQR ...
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  • 3,891
5 votes

Is configuration space same as joint space?

In robotics the configuration space is exactly the joint space of the manipulator. Differently, to indicate the space where the forward kinematic law maps the joints configuration into, we use the ...
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5 votes
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Configuration space of rotating link

Since the configuration space is the set of all possible configurations the link can have, i.e. all possible angles from 0° to 360°, shouldn't the c-space be a line rather than a circle? You are ...
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5 votes

A* search results in path too close to obstacles

Obstacle padding/ robot padding. Suppose you are working in a 2D environment and that you have an obstacle of the size 2x2. When doing planning (graph search, etc.), you increase the size of the ...
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5 votes
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How can Denavit-Hartenberg representation with only 4 variables describe rototranslations with 6 DOF?

In general you need 6 parameters to describe the position and orientation of any joint with respect to a link coordinate frame. The DH parameterisation includes 2 constraints so only 4 parameters ...
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  • 1,522
4 votes

Line following robot path planning

Line following is a simple reactive behaviour. Before you get into planning to solve the obstacle avoidance problem - which can get quite complex - you should consider simpler solutions. What this ...
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  • 2,954
4 votes
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How is homotopy used in planning algorithms?

Let me put homotopy into the context of planning algorithms Suppose you want to get from point A to point B. Clearly, the easiest way is to traverse a straight line. But if there is an obstacle in ...
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  • 1,238
4 votes
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Meaning of symbol, 'curly N' in the equation of Linear Gaussian system dynamics

They are modeling the probability as a normal distribution with the given mean and variance.
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  • 4,326
4 votes

Obstacle Avoidance while Navigating

I think that vector field histogram method should be a good solution here. It's a method of local motion planning (avoiding local obstacles while navigating to a global target). It involves mapping ...
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  • 953
4 votes

How can we solve the problem of robot size in sensor based motion planning?

If you are able to sense obstacles with a sensor pattern that is circular (eg laser scanner, contact sensors on a circular body, etc), and you can rotate the robot pose without translation, then you ...
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  • 4,235
4 votes
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Math behind trajectory planning

Since the problem is one dimensional, you are actually asking to compute a velocity profile. (A velocity profile is the information of how a path is traversed with respect to time.) Now the problem is ...
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4 votes
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Motion planning from a given path

Many articles reference algorithms such as A*, PRM or RRT based planners to motion planning algorithms which seems unreasonable since it is still necessary to parametrize found path with time.I wonder,...
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4 votes
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Velocity-Control of a manipulator without a dynamic model

Your intuition is partially correct in the sense that you ought to go with position control implemented via velocity commands resorting to a kinematic (not dynamic) model of the manipulator. This can ...
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4 votes
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What is the consquence of Gimbal lock?

I made a clip for you (https://imgur.com/a/KPeQ7Ia) using Unity, which internally represents rotations as quaternions, but uses Euler angles for display and positioning. You can see that, at zero ...
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  • 14.7k
3 votes

Optimal-time acceleration sequence of a line-following robot following a moving obstacle

The paper “Optimizing Train Speed Profiles to Improve Regeneration Efficiency of Transit Operations” (in JRC2014-3795.pdf) by Haichuan Tang et al addresses some of the issues mentioned in the question ...
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3 votes

Optimal-time acceleration sequence of a line-following robot following a moving obstacle

Assuming constant accelerations, "stopping" (slowing) distance can be calculated with: $$ x = x_0 + v_0 t + \frac{1}{2} a t^2 \\ $$ where $x_0$ is your initial position, $v_0$ is your initial speed, ...
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  • 14.7k
3 votes

redundant arm path planning and trajectory following

To expand on Alexandre's answer: Controlling the arm with the Jacobian along an end-effector trajectory is one way to do it. However, this will not give you obstacle avoidance. Although you could ...
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  • 5,215
3 votes
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State space and control space

The state space is the space of possible values that the state can take. For any given system it depends on which variables you are taking into account. For instance it is common to consider the 2D ...
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  • 3,891
3 votes
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Visibility Graph Toolbox for Python

The VisiLibity implementation appears to have python bindings.
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  • 306
3 votes
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Velocity Model Motion in Matlab (Probabilistic Robotics)

There are several traps you might have stepped into, but it is difficult to tell without more information. The first issues that came to my mind: The equations you wrote down are for sampling from ...
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  • 629
3 votes

What is the difference between path planning and motion planning?

There isn't really a difference. "Path planning" might be used more often to simply describe the problem of finding a desired path from one state (or sub-set of states) to another. Whereas "motion ...
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  • 1,357
3 votes

Lifting robotic leg with only one servo

Going forward, a Klann linkage has a near-vertical leg drop action. (See the legs at left in the wikipedia animated GIF.) It has a near-vertical leg lift action if running in reverse. (See the legs ...
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3 votes
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Check collision between robot and environment in OpenRAVE

It's really easy. ...
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  • 294
3 votes
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Suitable D star variant is for non-holonomic motion planning of mobile robots

A brief overview of some of these variants: A* A variant Dijkstra's algorithm that maintains a heuristic distance to the goal to first explore parts of the graph that are more likely closer to the ...
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  • 950

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