# All Questions

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### What is a simple way to assign frames to a robot manipulator using D-H convenction?

I am studying the forward kinematics for robot manipulators, and I am focusing on the Denavit Hartenberg convenction for assigning frames to the various joints of the manipulator. The problem is that ...
18 views

### Rotating a lever with a small servo

I'm trying to rotate a lever link to gently "offload" a load using a servo. Here's a drawing: Here, the red is a lever, yellow pivot and black is the load. To offload, the lever needs to be turned 90 ...
7 views

### Extrinsic parameters of an RGB camera - Typical procedure [closed]

I am new in the field of robotics and I would like to know what is the standard procedure for obtaining the extrinsic parameters of an RGB camera in the research community/industry. In my setup, I am ...
10 views

### Finding orientation angles of end-effector from the DH parameter table and transformation matrices

Let's say we have a manipulator with the following DH parameter table: and transformation matrices: A_{01}= \begin{bmatrix} \cos(q_1) & \sin(q_1) & 0 & 95\cos(q_1)\\ \sin(q_1) & -\...
12 views

### Mapping PID output to motors in 2WD line tracker

Recently at a small robotics design competition, a part of the challenge involved line tracking. Our implementation included six photo resistors on the bottom of the base and differential steering. ...
11 views

### Forward kinematics of spherical parallel manipulators with revolute joints

I found an article that can help in my investigations. Forward kinematics of spherical parallel manipulators with revolute joints The problem is solved for the following system of vectors, which is ...
17 views

### Finding Jacobian matrix using the DH parameter table and relative transformation matrices

Let's say we have a three revolute joint robot with the following DH parameter table: Where the last row corresponds to the transformation between the last joint frame and the end-effector frame. We ...
17 views

### Ceiling Camera & robot - SLAM still neded?

I've got a question regarding the topic of SLAM. My composition consists of a mobile robot and a top down looking 2D camera with wide-angle lens. It is comparable to a survaillance camera mounted on ...
13 views

### Which development board should I go for while making a manual robot? [closed]

I'm planning to make a robot for ABU Robocon 2020 which is supposed to have the following parts: 4 x DC motors (with mecanum wheels) 1 x High RPM DC motor Wireless receiver for controlling the motors ...
19 views

### Non-linear MIMO system inverted pendulum controller [closed]

We have a big problem. We are trying to work on a controllable inverted pendulum, however we are stuck. We want to control all angles, using the fact that we can control all torques. The differential ...
18 views

### Is SLAM done only first time in a given environment

I am training Turtlebot 2 to move around the office. I come from robotics hardware background but relatively new to computer vision and robotic mapping. Here are my two fundamental questions related ...
15 views

### how to communicate vrep with ESP8266 via wifi to send and receive data

I'm looking for some guidance on a project that I've been doing for quite a long time; the project is about a 4WD robotic platform for obstacle avoidance with haptic feedback. if you know about the ...
27 views

### Collaboration of mobile robot and survaillance camera - classic localization (still) needed?

Just started with the topic of mobile robotics.. so I'm still into concept making and little programming, but have not setup everything or tested at all. I got a (differential) mobile robot (lego ...
13 views

### How do I calibrate a rotating laser scanner pose from known global coordinates?

Assume the following scenario: A 2D LIDAR sensor is mounted with a vertical (not exactly known) scan plane at a height of 20m The scanner can be rotated about the vertical axis and the encoder values ...
15 views

### Which is the recommended depth estimation method for under vehicle scanning?

There are many ways to estimate depth e.g. Structural light based solutions Time-of-flight (ToF) cameras LiDAR Stereo cameras Computer Vision image based methods Monocular models such as monodepth2 ...
32 views

### Fusing IMU sensor with odometry

Would fusing Odometry estimation with IMU sensor increase the accuracy of estimation for planar differential drive robots?
30 views

### How does scan matching find overlapping regions in two scans?

I have been reading about scan matching and so far I have gathered that scan matching tries to find the transformation (rotation and translation) which leads to the best match between overlapping ...
45 views

### Wall-E Legs mechanism

I was trying to understand the mechanism of Wall-E's Legs from the Wall-E 3D animation movie of Pixar Animation Studios, how he is able to move up and down and move the tracks on all directions. Can ...
17 views

### implement torque control on a robot with some joints supporting torque control while others only supporting velocity control [closed]

I have a robot, some joints of which supports torque control,while the rest only supports velocity control. What should I do to implement torque control on the whole system?
12 views

### Google Cartographer: bag validation detects gaps in LIDAR messages

I'm using google cartographer to do SLAM, and I'm experiencing some accuracy issues, in particular my map rotates and gets distorted when the robot rotates. I run ...
44 views

### Some Kalman filter implementation queries

Just to clear some doubts: Qn 1. Does kalman filter require constant time step? From my own study, it does not seem necessary to have a constant time step. You just need to take into account time ...
47 views

### Using gyroscope to calculate forward kinematics

I want to measure the end-effector position of the robot that I attached. I'm using both gy-25 and gy-521 for calculation of the angle. As shown in the picture, joint 1 has 2 DOF, one for spatial ...
23 views

### Interpreting results from Camera Calibration?

I used OpenCV's findChessboardCorners on a few checkerboard images (40~) and about 27 seemed to find the corners accurately. How does one proceed from here? Do I calculate the reprojection error over ...
19 views

### BLDC Outrunner Direction Change?

I'm designing a Quadcopter for my project. I've seen a lot of guides that the motor rotational direction should be opposite to each other. My doubt is whether the motor have a variety of CW rotation ...
38 views

### What are some recommended mathematical courses to understand robotic systems? [closed]

I would like to know what mathematical courses would help me understand robots better. Certain mathematical concepts seem important to know because I have heard roboticists talking about them. For ...
48 views

### Why are the angular velocities of concentrated masses in Lagrangian independent?

There is an ordinary linear three-mass system. If we write its Lagrangian, we get the following equation. where $W_k$ and $W_n$ - kinetic and potential energy. To find the moment of rotation of the ...
59 views

### How to calculate the maximum charge of the battery?

How to calculate the maximum charge of the battery that it can give from a fully charged state to a fully discharged one. I have been trying to solve this problem for 2 months. The drone itself is not....
15 views

### How To Do path planning To move the Robotic Arm in straight line in 3D where the arm is having base, Shoulder, Elbow & wrist? [closed]

Now the design we have has the 4 DOF (Base, Shoulder, Elbow, Wrist), there is no problem in moving the arm in a curved manner but the main problem arises in straight-line motion. I'm unable to fid=nd ...
29 views

### Robot-telescope prototype controlled by a PC

Has anyone developed mechatronic systems for DIY-telescopes running a PC? Please share your experience, knowledge and nuances (how you acquired current sensors, speeds, electric motors, about ...
53 views

### Dynamic models of parallel robots in the form of multi-mass systems with stiffness coefficients

I want to develop a dynamic model of a parallel robot for control tasks. It is known that equations of motion based on Lagrange equations can be transformed into a state space and use such a model. ...
32 views

### Yaw, Pitch, Roll rate concepts and how to calculate them with an IMU

I need help understanding the difference from Y/P/R rate and the data that I can get from a gyroscope. I am using the raw readings of my IMU (MPU9250) and the Madwick Filter to calculate a quaternion ...
29 views

### Drone Horizontal Speed Measurement

Assuming no GPS is available, what can be used to measure the horizontal speed of a hypothetical drone? Sensor mass and size don't need to be taken into account. Could small Doppler radars , maybe ...
20 views

### MPU6050 Gyro rotaion always around Y axis

I am using an MPU6050 IMU. I did a small experiment having Z-axis pointing upwards. 1. Rotate 90deg around Z-axis (yaw) and back to the original position 2. Rotate 90deg around X-axis (roll) and back ...
42 views

### Yaw from IMU acceleration

When IMU is gravity aligned, yaw is not observable from linear acceleration data. However, when IMU has non null pitch, the sensor is not gravity aligned anymore and the gravity acceleration gets ...
31 views

### Robotic vision eye-in-hand research

I started researching Robotic Vision topics for a while but I found myself a bit stuck. My background is in the Computer Vision and Machine Learning fields but I lack the knowledge in robotics. My ...
40 views

### Stepper can't turn plastic wheel. Is it normal?

Is it normal, that a stepper motor with the following specifications can't reliably turn a plastic wheel with a diameter of 13cm and a simple direct coupling? Type: bipolar, two phases Voltage: 2.55V ...
22 views

### How to make small quantities of gears

For a hobby project, I'm designing a clock with a single hand that makes one revolution per year. Using really helpful sites like https://geargenerator.com/, I have the gear ratios and dimensions ...
62 views

### Modeling of Robots

There are mainly two approaches for controlling robots (mobile robots and static robots): 1) working with kinematic equations, controlling joint or wheel speeds , 2) working with dynamic equations and ...
37 views

### Can I apply a common voltage to a high speed running DC motor to stop it? Will it damage the DC motor?

I decelerate the velocity of my robot very quickly by applying a common voltage (eg. 24V to both the terminals using Motor driver) to the DC motors. Given, the motor is running at a very high speed ...
20 views

### How do I say if a system is differentially flat?

I am studying mobile robots, and I have encoutered the concept of differentially flat systems. I have seen that if a system is differentially flat, we can identify flat outputs, thanks to which we can ...
26 views

### path planning by means of geometric map

I'm having trouble understanding how to use geometric map in path planning task using algorithms like potential field or elastic band which I always see use occupancy grid. By geometric map I mean a ...
26 views

### Doubt on artificial potential field

I am studying motion planning, and I am focusing on artificial potential fields. I have seen that it consists in having a repulsive field for obstacles, and an attractive field toward the goal. But ...
44 views

### When do I do motion planning?

I am studying mobile robots, and I am focusing my attention to the unycicle. I have a doubt concerning the motion planning part. In particular I don't understand when the motion planning is done and ...
11 views

### Extract Coriolis matrix from Coriolis*q-dot vector multiplication

I have been using matlab to do some robotics simulation. I am able to Create the forward kinematics with transformation matrices Create the jacobian matrix Find joint velocities Create the ...
41 views

### In a Kalman filter, what should be included in the state, and what should be included in the control?

Let's say I am controlling a robot using a velocity controller. This involves specifying a target velocity for the motors, which is achieved using a PID controller (the low-level details of this PID ...
42 views

### State-dependent Covariance in the Kalman Filter

When using a Kalman filter, one of the variables that must be defined is a matrix representing the covariance of the observation noise. In the implementations I have seen, this matrix is defined once, ...
15 views

### Dynamixels (AX-12A) no longer detected after id change

I have 8 dynamixels that are connected together. Everything worked fine until I changed all their ids to 200,201,202, ... To change their ids, I used this python library. Now, none of my motors are ...
85 views

### Angular velocity in terms of quaternions

Im reading Theory of Applied Robotics, 2nd edition by Jazar, specifically section 7.1, example 207 on page 390. The author is trying to express angular velocity by unit quaternions. Starting from ...