# All Questions

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22 views

### How to avoid hair entanglement in your robot wheels?

This isn't about any complex math or physics of robots, but rather an annoying practical issue I don't find much information about. My robot works indoors (house, office) and there's certainly going ...
12 views

### Using Scratch with Waveshare Alphabot pi robot

I am trying to find out if and how i could use Scratch to control Waveshare's Alphabot kit. I want to be used as an entry level robotics training for kids 8-10 that already manage standard Scratch. ...
33 views

### Kalman Filter for 2d pose

I'm really sorry if this is a dumb question, but I don't have a clue on how to do this. I'm trying to write a kalman filter with a State vector of : {x, y, ẋ, ẏ, ẍ, ÿ } To estimate the 2 dimensional ...
12 views

### Drone based CV via base station - power requirments

Currently computer vision based inference is impractical on a drone given the significant power draw. Is connecting a drone to a base station which does CV a viable solution to this issue? Has it been ...
18 views

### 2D Visual-Inertial Extended Kalman Filter

I am trying to implement an Extended Kalman filtering for combining IMU data and visual odometry in a simple 2D case where I have a robot that that can only accelerate in its local forward direction ...
18 views

### Does an S type load cell need to be loaded perpendicular to its screw holes?

I know that a bar type load cell needs to be setup as shown here as to flex the strain gauge However, most tutorials or guides show how to setup an S type load cell like this (for tension) and not ...
28 views

### Does every rotation vector has an one-to-one corresponding rotation matrix?

Given a rotation vector, can we always get the same corresponding rotation matrix computed by the Rodrigue's rotation formula?
15 views

### Applying Rotation & Translation Matrix Obtained from Iterative Closest Point

Suppose I have M lidar contour points from t = k and N lidar contour points from t = k+1. (Some of you might question why I have differing number of contour points, and the reason is that these lidar ...
12 views

### Controlling high torque servo motors with Raspberry Pi

I need to control 10 Standard Servo Motors (operating at 4.8-7V/300mA-1A/2.5kg-5kg torque) in my project. I'm using RPi as my processor and I was looking for a servo driver. I came across PCA9685 16-...
14 views

### Can someone share with me some modern review paper about the filter-based SLAM?

I'm currently learning the Visual SLAM. But I'm also very curious about the modern filter-based SLAM. Can someone share with me some modern review papers about it?
10 views

### Compute absolute position of obstacle in V-Rep from proximity sensor measurement

all. I am trying to construct the map of the environment by using the measurements from the proximity sensor in V-Rep. I have absolute position of the robot. So, I know the X1, Y1 coordinates of the ...
27 views

### Counterweight in arm designs

I wonder why most robotic arms use large J2 (shoulder) motors rather than counterweights. What sort of complexity do they add to the design beside increase in overall weight? In fact, rather than ...
13 views

### RLException: neither a launch file package nor a launch file name

To get straight to the point I want to know how to fix this error and understand it, what is an RLException? Why am I getting this? How can I avoid this later? Below I will post what I did step by ...
24 views

### Help with 2D forward kinematics

I have been trying to find the HTM of a 2-DOF arm in 2D by finding the rotation matrices and displacement vectors by hand rather than use DH parameters to better understand them. I have followed the ...
39 views

### Get Topic values in script

Hi i am doing an apriltag following project. I am currently trying to test how to get distance between the tag and the camera. I have subscribed to the AprilTagDetectionArray msg. My main question is ...
27 views

### How is the depth estimation done in DTAM / LSD-SLAM (direct VSLAM)?

I know that DTAM and LSD-SLAM both employ the photometric error between two keyframes to estimate the image depth. But I don't know what the photometric error describes precisely. In the DTAM paper, I ...
31 views

### What is an example of a good motion control API?

We are in the process of implementing a motion control API for a research project. The goal is to implement a somewhat comprehensive API for motion control that provides the most commonly used ...
19 views

### T200 thruster motors / Blue robotics

I have (4) T200 thruster motors, I want to run all four at the same time with a servocity joy stick controller, I have been running (2) motors with a Y splitter but now want to run (4) motors with the ...
29 views

### Angular movement of a controlled arm relative to an object via Two IMUs

I've been tasked to use two YEI 3-space sensors (IMUs) to detect the azimuth and elevation (altitude in the image below) angle of a moving arm with respect to a fixed object, with a sensor on the end ...
47 views

### Kalman filter with missing dimension on measurement input

I am exploring the option of using a EKF with my differential drive robot. I do not have any prior experience with kalman filters. The robot that is under consideration has two wheel encoders for ...
23 views

### Gimbal motor shaft

Does anyone know if a shaft can be pressed into a gimbal motor like this? Is the centre metal ring just the inner race of a ball bearing? The ring looks thicker on one side but thinner on another ...
70 views

### Assistance in finding correct LIDAR for short-range object detection task

I am working on a task that involves finding a distance of a moving object going a static linear object, e.g a long pole. After trying some approaches (mostly involving stereo vision), I have come up ...
21 views

### How do you handle angle discontinuities in estimation problems?

When one is implementing a state estimator in a system that involves kinematics, will inevitably face the problem of angle discontinuities, i.e., the fact that the angles have to be wrapped between ...
41 views

### How do I get competent in using c++ for my projects? [closed]

I am a PhD student, working on Sensor Fusion and estimation problems. I would like as I finish my PhD to have acquired sound knowledge in what seems to be the industry norm for working with real ...
13 views

### Triangulation in Stereo-Vision?

I need some help in 3D Positioning system I'm trying to set up. At the moment I am using 2 Calibrated cameras, my strategy is to place an AR Marker on the scene, identify the position of the AR Marker ...
22 views

### Given this old pin diagram and numbers on this old encoder, what would be a suitable modern encoder to use?

My place of work has recently acquired a Hydraulic Press Break from the 80's. It has a CNC controlled back stop which is driven by a DC motor and Screw drive. The encoder which couples to the motor ...
23 views

### Custom implementation of robot_localization package

I plan to implement a sensor fusion of IMU + Visual odometry using an EKF. I came across the excellent robot_localization package which does pretty much all that I want. However, I need to use perform ...
30 views

### Occupancy grid maps

Why do we take probabilistic approch to model the environment for robots in occupancy grid maps.The assumption is always taken that each cell on the grid map is either free or occupied.So why have ...
23 views

### Angular rate controller

I try to design an attitude controller with cascaded PD-P structure (angle-angular rate) for well-known quadrotor dynamics according to the thesis. I use an imu as expected in order to get the angle(...
22 views

### ICP(Iterative Closest Point) with Partially Overlapping Conditions & Changing Point Numbers

I am currently working on fixing vehicle odometry data using lidar contour points. Since I am receiving lidar data in the form of countour points, I thought I'd use ICP to correct the odometry error ...
16 views

### Vehicle Odometry Correction Using Lidar Contour Points (Localization)

I am currently working on a project where... Vehicle travels from point A to B GPS trajectory is used as a reference Vehicle odometry (bicycle model without slip angle beta) was used to estimate a ...
26 views

### Bias correction for multiple sensor fusion through Kalman Filtering

I am learning Kalman Filters and was working on a simple example: Temperature measurement of a room by using 4 thermometers(different biases and noises) if i consider that there is no bias in the ...
18 views

15 views

### Why cant the Controller Spawner find the expected controller_manager ROS interface?

I have a quadruped robot with base link (BL), 4 child links called LFT,LFT, RFT,RFT, T for thigh and each having 4 children with name LFC,LBC,RFC,RBC, C for Calf. 8 joints - Base link to 4 thighs and ...
25 views

I attached two quadrature optical encoders to the wheel of the mobile robot. I also have imu6050 attached to the breadboard to calculate the orientation of the wheel mobile robot localization. I want ...
45 views

### Compute path in absolute frame from sequence of measurements

I have a sequence of measurements $\{(x_i, y_i, \theta_i)\}_{i = 1 \:...\: N}$. Each of these represents the new pose of the robot seen from the previous pose, i.e. a measurement $(x', y', \theta')$ ...
11 views

### Point of origin in stereo-calibration OpenCV?

I set up a stereo-vision system to triangulate 3D point given two 2D points from 2 views (corresponding to the same point.) I have some questions on the interpretability of the results. So the size ...
9 views

### Wrist's displacement calculation with IMU

My project is about to track the writer's wrist movements with IMU ( with a 3-axis accelerometer, gyro, and magnetometer). I have seen some claims that tracking object in 3-axis is not an easy task ...
18 views

### Motion model and homogeneous transformation issue on a drone

I am trying to develop a EKF-SLAM algorithm for a drone, and I want to estimate its position in the inertial/world reference frame. I have as control variables the linear and angular velocities in the ...
31 views

### How to calculate the pitch of the quadcopter rotor blade and their efficiency

I have gone to some of the blade designs and profiles of the blade which suits my requirement. But, once after entering the Theoretical calculation, I was stuck in the determination or the ...
14 views

### Stereo depth error correction

The depth error for a stereo camera is given by: As the depth increases the error increases quadratically. I'm wondering if there's a way to model that error and then correct the estimate. On my ...
10 views

### problem in understanding this part of the RRTx path finding algorithm

this is a paragraph from the paper of the RRTx algorithm and below it a figure referenced in the paragraph however the No and Nr nodes types are unclear to me what are they exactly ?
32 views

### Cartesian Angular Velocity

Let's say I have a Jacobian which gives the relationship between the velocity of a robot's joints, and the Cartesian velocity of its end-effector, relative to the end-effector's local frame. And let's ...
10 views

### ModuleNotFoundError: No module named 'second.core.non_max_suppression.nms'

I am using Anaconda base environment for second.pytorch of ubuntu 16.04 after executing the following: nvidia-docker run -it --rm -v /media/yy/960evo/datasets/:/root/data -v \$HOME/pretrained_models:/...
18 views

### Are there some papers or books that compactly elaborate the essential part of the multiple view geometry?

I am a novice to visual SLAM and computer vision. Recently I've read a paper "A micro Lie theory for state estimation in robotics" dedicated to introducing the essential part that necessary to ...
32 views

### design optimization method using indices

there are several methods like manipulability and conditioning index for design optimization kinematics performance, but these methods rely on the singular values of the jacobian matrix. i described ...
30 views

### Implementation of a particle filter algorithm

How do you calculate the likelihood of making an observation ? Does someone have a link to a book or article that explains the math that you need to do to implement a PF algorithm? Conceptually i ...
9 views

### ROS2 and TypeError when publishing custom message to Topic

I have defined a custom message: uint8[] data The custom message is imported in my Node class with no problems: ...