# Tag Info

### 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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### 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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### 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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### 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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### 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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### What is the difference between motion planning and trajectory generation?

Sometimes the two words are used interchangeably. However, there are some subtle nuances between motion planning and trajectory generation. When talking about motion planning, it is planning motions ...
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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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### 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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### 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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### 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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### 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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### Motion profile and Motion control scheme, how do they interact?

These two concepts are complementary and you use them together, the motion profile providing the input to your control scheme. At each time-step the motion profile gives you the reference values for ...
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### What is the consquence of Gimbal lock?

I made a clip for you (https://i.stack.imgur.com/Z0q5Y.jpg) using Unity, which internally represents rotations as quaternions, but uses Euler angles for display and positioning. You can see that, at ...
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### Path planning for visual servoing

I would recommend using an RRT or FMT sampling based path planner. The basic idea is to sample your state space and build a tree which connects your starting state to the goal state. Each time you ...
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### Meaning of s_last in D star Lite algorithm

$s_{last}$ does change. Looking at the pseudo code, $s_{last}$ is updated upon each iteration of the while loop in main(), in ...
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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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### RRT algorithm in C++

The OMPL library has some good quality implementations of several sampling-based motion planners, as listed here : http://ompl.kavrakilab.org/planners.html In particular, you can find several ...
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### Motion planning and robot controlling

The model you have given is called the unicycle model and is widely used n robotics. In general the model is given by \begin{eqnarray} \dot{x} &= v\cos \theta \\ \dot{y} &= v\sin \theta \\ \...

### Optimal-Time Trajectory Planning in 1D

Hi usually the time optimal solution of a motion not having specific constraints is know as 'bang-bang'. Where you let you system accelerate and decelerate at the maximum rate possible. In your case, ...
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### Creating linear end effector motion using joint speeds: Converting tool speed to joint speeds

Joint velocities and tool velocities are directly related through the following equation $$\dot{x} = J(q)\dot{q},$$ where $\dot{x} \in \mathbf{R}^6$ is the tool (linear and angular) velocities, \$\...
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### A* search results in path too close to obstacles

Most planning algorithms reduce your robot to a point and plan a path for that point. The arising problem is exaclty what you are facing. As suggested before, obstacle padding is one of the methods, ...
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### What is the difference between Obstacle Avoidance and Dynamic Path Planning?

I have lots of experience with this that I won't bother you with. Most vehicle planners have multiple layers, with different requirements. In short, you're right in that they are very closely related ...
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### Is there a Java or mathematical algorithm for Pure Path Pursuit?

In words, rather than code. Assume you have the path defined as a dense list of points. Find the point on the path closest to robot Draw a circle of radius R about that point, then find the point on ...
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### Motion Planning vs. Control

I can speak to space robotics, and military-type robotics, and some commercial robots, but there isn't really a "typical" robot yet. How does motion planning differ from controls? A drunk ...
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### Applications of Reinforcement Learning

It's true that using RL in robotics involves many challenges, including the usually high dimensionality of problem spaces, the cost and limitations of real-world sessions, the impossibility or ...
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### RRT algorithm in C++

The first hit on GitHub gives me the following implementation, which is what you seem to be looking for. https://github.com/RoboJackets/rrt
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### Applying MoCap data to real life robot

Chuck's answer is correct; applying motion capture to a robot will make its legs move in a walking motion, but won't guarantee that the entire setup will remain upright. One simple fix for that ...
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### Applying MoCap data to real life robot

Yes, you could control the legs, but no, you're probably not going to get the effect I think you're after. The legs will probably not walk on their own just because they're miming what your motion ...
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### why is quadrotor motion planning hard?

The main problem with motion planning is the time-dimension. Not only that the UAV can move up, down, forward or backward, but the motion is also defined along the time-axis. A motion plan like "up, ...

### ROS MoveIt!, virtual joints, planar joints, prismatic joints

I am assuming that what you want is to to move the eef to any pose in the workspace by moving the robot's base. If this is the case please refer to the Inverse Reachability Module by OpenRave like @...
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