Brian Lynch
  • Member for 6 years, 3 months
  • Last seen more than 5 years ago
What is $\alpha \sin(\theta) + \beta \frac{d \theta}{d t}$ in the inverted pendulum problem?
8 votes

The function $f$ comes from the equation of motion for the inverted pendulum problem (inverted pendulum alone, not including the motion of the wheeled platform). If you consider your figure but ignore ...

View answer
Designing a 5 bar linkage robot: Plot Clock
Accepted answer
8 votes

Both the forward kinematics and inverse kinematics aren't too difficult, but always a little tricky for parallel manipulators like this one. Consider the configuration in this diagram. The forward ...

View answer
Relation between pole placement and marginal stability?
Accepted answer
6 votes

You are most likely running into problems with the maximum time step in your simulation. This phenomenon is known as stiffness, where your equations of motion are highly sensitive to the size of the ...

View answer
Length and Width of a Line Following Robot
Accepted answer
5 votes

Actually, the caster wheel has ideally no effect on the kinematics of the vehicle. In reality there will be some resistance from the caster wheel that does impact the vehicle motion, but we can still ...

View answer
Pole-balancing / inverted-pendulum; is there a need for active control?
5 votes

Your question might be better suited to another forum, but is definitely important for robotics in general. You are basically talking about unstable equilibrium, where there does exist a point where ...

View answer
What is torque bandwidth in actuated joints and how does it affect the control systems?
Accepted answer
5 votes

The torque bandwidth is typically referring to the maximum frequency of motion at which the actuator can provide that torque. So your actuator can provide a peak torque of 100 Nm, as in it can hold up ...

View answer
How to use SLAM with simple sensors
4 votes

The actual implementation of SLAM won't care about whether you are using high fidelity laser range finders or cheaper ultrasonic sensors. Both are providing range measurements with the biggest ...

View answer
ROS and Kinect data without callbacks
3 votes

You should simply use the callback method since you can have an object in your code that is always updated with the latest measurement. Then you can simply poll the measurement in that object whenever ...

View answer
Getting pitch, yaw and roll from Rotation Matrix in DH Parameter
Accepted answer
3 votes

In general, Euler angles (or specifically roll-pitch-yaw angles) can be extracted from any rotation matrix, regardless of how many rotations were used to generate it. For a typical x-y-z rotation ...

View answer
Trying to calculate the Thrust of my quadcopter motors
3 votes

Your motors do not develop the thrust, they spin rotors which develop thrust. Practically speaking, it is probably better to create an empirical model (or look-up table) based on measurements of the ...

View answer
Transforming angular velocity?
Accepted answer
3 votes

I think your diagram is missing an angle for the laser angle with respect to the vehicle body -- I'm going to call that angle $\alpha$, see this diagram for clarity: Since it seems you are tracking ...

View answer
What is the difference between path planning and motion planning?
3 votes

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 ...

View answer
Where should I put the angle sensor on my cart-pole robot?
3 votes

The gyroscope placement shouldn't make any difference since the rotation rate will be the same everywhere (assuming your robot is rigid enough). The accelerometer will pick up the rigid body ...

View answer
what's confidence level? and how can we use it for vehicle detection using OpenCV?
3 votes

Statistical confidence is most often defined in terms of a score that is the number of standard deviations away from the mean. Now let's say you have a set of states (a state vector) used to define ...

View answer
Overcorrecting Kalman Filter
3 votes

There is an error in your posted equation for the Jacobian $F_J$, so that could be the source of the problem. It should look like this: $F_J = \begin{bmatrix} 1 & 0 & -C \sin \theta \\ C \...

View answer
Real-time camera localisation in known environment
2 votes

The problem you want to solve is definitely a SLAM problem and not just simply localization (or maybe we can consider it SLAm since the mapping part is not as heavy). The reason for this is that you ...

View answer
Is it possible to design robot software or AI to function in different devices?
2 votes

This already happens when a commercial robot product comes off of the assembly line! The robot software is the same for each robot and is copied over. Some robots work using similar computer ...

View answer
Lifting robotic leg with only one servo
Accepted answer
2 votes

The linkages suggested by jwpat7 are great, and I would probably prefer to use something like that. But, if you want something really simple, then you might be able to get away with a four-bar linkage ...

View answer
Kinematic decoupling
2 votes

Kinematic decoupling really depends on the configuration of your particular manipulator. When you decouple the wrist, it is typically so that you can take any given end-effector pose and determine the ...

View answer
Using an RGB + Depth Camera to locate X,Y,Z coordinates of a ball
Accepted answer
2 votes

The critical part is the registration between depth data and RGB data. If the registration is calibrated properly then you can just extract the depth for the particular target pixel (X,Y), using ...

View answer
Filtering IMU angle discontinuities
Accepted answer
2 votes

Here are my two suggestions for dealing with this problem: Use a median filter, which replaces each value of your signal with the median of the values in a small window around each one. Here is some ...

View answer
Is modelling a robot and deriving its Equations of Motions more applicable to a system that is inherently unstable?
2 votes

The inverted pendulum is unstable in the sense that it will diverge away from the upright position if perturbed (for example, slightly blown by wind or lightly vibrated). On the other hand the "...

View answer
What is the required theory behind building a robotic arm?
2 votes

It sounds like you are developing a robotic manipulator from scratch so I also assume you will be writing software for position control too. Both the design and control depend on not only the dynamics ...

View answer
DC Motors for a ROV?
Accepted answer
2 votes

The main differences between brushed and brushless DC motors are cost, efficiency, and complexity. Brushless motors don't have brushes (surprise!) so they don't wear down as fast as brushed motors and ...

View answer
Is Venetian mirror possible in Autodesk Inventor?
Accepted answer
1 votes

Surface properties like that are really only for cosmetic purposes so it is unlikely any CAD program has that option. However, you may be able to get the appropriate effect by assigning particular ...

View answer
How to connect absolute encoder on the rotating shaft. Please see the three options?
1 votes

Most gear motors with integrated encoders have them placed on the motor shaft, which allows for much finer angle resolution at the output but does not account for backlash. I think this is what you ...

View answer
Mapping between camera pose and image features in visual servoing
Accepted answer
1 votes

Image features are connected to the camera pose through two steps: (1) the relationship between the feature pixel coordinates and its homogeneous coordinates in the camera reference frame, and (2) the ...

View answer
Relative orientation of two robots
Accepted answer
1 votes

Applying the rotation sequence (x-y-z) that you specify, your first robot tool will have the following rotation matrix: $R_1 = \begin{bmatrix} 0 & 0 & -1 \\ 0 & -1 & 0 \\ -1 & 0 &...

View answer
Electronic circuit for heating nylon fishing line muscle
1 votes

For a heating element you want lower resistance -- remember $V = I R$, so high resistance means lower current, and that in turn means lower power for the same applied voltage since $P = \frac{V^2}{R}$....

View answer
Angular velocity to translational velocity
Accepted answer
1 votes

Overall, you simply need to rotate each point in your cloud using the rotation matrix $R$. That rotation matrix will be the latest rotation matrix for your vehicle/sensor. You can compute the rotation ...

View answer