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2015-03-31 06:16:51 -0500 asked a question Robot Oscillating Wildly When Attempting To Drive

Hey, so my robot is acting rather strangely when trying to control it. I have attached a differential drive controller. Driving forwards or backwards in a straight line everything works fine, but as soon as I attempt to turn the robot goes crazy and begins wildly oscillating around the world. Any ideas on what could cause this?

I sometimes also get the same sort of problem when adjusting some of the joints

Thanks in advance!

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2015-03-26 12:26:01 -0500 commented question Adding torque sensors to my robot

I believe this link would have have a nice solution, I found it in an earlier question however is it now dead

2015-03-26 11:03:28 -0500 asked a question Adding torque sensors to my robot

Hello, sort of new to this stuff. Currently I've build a .Xacro for my robot which works quite nicely, now I want to attach some torque sensors to the joints to get some readings. I don't really know whats the best way to go about this and if someone could point me in the right direction it would be awesome!

Thanks in advance

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2015-03-24 10:18:04 -0500 commented question Joints won't hold in place

What I ended up having to do to get around this was to launch my controllers simultaneously and have their signals hold the joints where i wanted them to, still not convinces this is a perfect solution as I believe I require some sort of friction value in the joint itself which would hold it in place without the need for controllers.

2015-03-24 10:16:27 -0500 asked a question Tuning PID values: erratic responses

Hello again,

Having some trouble with joints in my robot. Basically I've been tuning the PID gains for certain joints to get a good response from the input and I have found two problems. One is that the P values required for lifting a prismatic joint vertically upwards and match the set point is extremely high, ~2000, not sure if I'm doing something wrong here but any tuning I've done previously has never had such high values.

Secondly I'm looking for a way to smooth out the response in both directions. As my joint is vertically orientated the upwards response happens much slower than the downwards response, which I assume is due to gravity. How can I make my response more similar in both directions?

Thanks in advance!

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2015-03-23 12:00:16 -0500 asked a question Joints won't hold in place

Not really sure what i should be doing with my model, i have a prismatic joint which slides downwards due to gravity. What I want is for somehow the joint to not slide down to its lower bound before I can attach my controllers which will determine its positional value. I tried giving the joint friction using dynamics tags in the joint properties in the URDF.

Any ideas how to fix this problem

2015-03-23 11:55:09 -0500 commented question Mesh Scale Huge for .stl file

I dont really know what was causing this, maybe the fact that the solidworks model was developed in mm rather than m, i ended up just using a scaling tag and setting the three parameters to 0.001 and it imported fine

2015-03-19 15:10:07 -0500 asked a question Mesh Scale Huge for .stl file

Hello, having a problem where the meshes which i'm importing to my URDF file are absolutely huge. The dimensions are correct in solidworks (around 400mm cube). I tried changing the units of the part back to meters as i was working in mm and this had no effect. Any idea what i'm doing wrong?

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2015-02-15 11:56:08 -0500 asked a question Spawning Robot Problem

Hello, so the problem I'm having is most likely due to my inexperience with the software, hopefully a push in the right direction will get me on my way. I have created my own URDF file for a robot, the robot is close to humanoid in shape. When making the URDF file, I developed it so that the robot would be standing perfectly upright this allowed me to give coordinates in the XZ plane making them much simpler. Now, my problem is that the robot actually rests in a sort-of kneeling position so what I have done is make many of the joints revolute and made the upper and lower very close, basically fixing the joint in another position. This worked fine when creating the file n Rvis. When I bring it into Gazebo it appears as though the robot spawns in the standing upright position as the URDF was created for but then very quickly changes to the position specified by the revolute joints, which appears in turn to give some sort of momentum, throwing the robot around. Are there any simple ways to resolve this?