View Full Version : Xan's Rover with Arm

03-18-2009, 03:21 AM
Hi All,

I’ve been working on this project for a couple of weeks now. The project includes a A4WD1 Rover (http://www.lynxmotion.com/Category.aspx?CategoryID=118) with a AL5B Arm (http://www.lynxmotion.com/Category.aspx?CategoryID=126) mounted on top. The arm got a total of 6DOF controlled using IK.

Hardware setup:
A4WD1 Rover (http://www.lynxmotion.com/Category.aspx?CategoryID=118)
AL5B Arm (http://www.lynxmotion.com/Category.aspx?CategoryID=126)

Bot Board 2 (http://www.lynxmotion.com/Product.aspx?productID=252&CategoryID=66)
Basic Atom 28 Pro (http://www.lynxmotion.com/Product.aspx?productID=468&CategoryID=66)
Sabertooth (http://www.lynxmotion.com/Product.aspx?productID=563&CategoryID=10)
6V 2800mAh NiMH battery for logic and servos (http://www.lynxmotion.com/Product.aspx?productID=426&CategoryID=48)
12V 1600mAh NiMH battery for the wheels (http://www.lynxmotion.com/Product.aspx?productID=64&CategoryID=48)

I started out by stripping my phoenix code (http://www.lynxmotion.net/viewtopic.php?t=4285) down to a single leg and added the wrist in the IK calculations. The arm IK is calculated in 2D and includes shoulder, elbow and wrist servos. The gripper, wrist rotate and base are directly controlled by the remote. I’ve also tried including the base in the IK to get 3D control but this wasn’t easy to control with a remote.

There is no SSC used in this project. The 6 servos are driven by a interrupt routine which makes it possible to do group moves and control both positions and speed with the BAP. Because the servos are controlled with the use of interrupts it is possible to drive the servos and do IK calculations at the same time. I used a program from Nathan (AcidTech) as example for the group move. Can’t find the link so I’ll post that later on.

Time for some pictures!



The video is showing the current status. here


03-18-2009, 07:12 AM
Pretty fun grabby bot. Any plans to have it detect and grab objects on its own?

03-18-2009, 08:09 AM
Looking good Xan!

Great work with the kinematics and control (as always ;)). Are you planning of adding force sensor to the gripper?


03-18-2009, 08:20 AM
Great looking bot xan. Keep up the good work.

03-18-2009, 10:34 AM
Hi Guys,

Thanks for the quick replies! I really appreciate it!

Pretty fun grabby bot. Any plans to have it detect and grab objects on its own?
Not yet but it sounds like fun! Iíve got some sensors lying around which should be able to do the job. What should be better to use on this, ultrasonic or GP2D12 IR sensor? I saw Laurent from the LM forum do some crazy stuff with it (http://www.lynxmotion.net/viewtopic.php?t=1139&highlight=3d)! Iím not thinking of mounting the sensor on the arm but on the base with maybe a servo to scan horizontal. I might get back on this. :)

Are you planning of adding force sensor to the gripper
Iíve got some spare FSRís as well. I think Iíll add this soon because I think this will keep the gripper servo from gripping to hard and overload. Not that it happened but it bends and makes a lot of noise when I stop it to late.

Great looking bot xan. Keep up the good work.


03-23-2009, 03:44 AM

Both you and the guys from TR gave me some good ideas. So Iíve spend most of the weekend adding stuff to my rover. :)

Iíve added a FSR to the gripper as described in this (http://www.lynxmotion.com/images/html/build129.htm) tutorial. The gripper now stops when it grabs something so I donít need to worry if I hold the close button for to long.

Robologist, You've got it started. Youíre question kept me busy this weekend! 8) Iíve added a single servo on the front of the rover. The servo rotates a IR sensor (http://www.lynxmotion.com/Product.aspx?productID=260&CategoryID=8) to scan the front for objects. The servo divides the range in 40 steps. It measures the distance with the IR sensor. If the object is wide, it canít be moved so the rover turns. If the object is narrow enough for the gripper. It tries to move it.

Iím also planning to add a IR sensor on the gripper to check the height from the object before it throws around my furniture. :P

With the IR sensor mounted the AL5B wouldnít give me enough range to grab stuff from the round. Iíve replaced it with the AL5D. The looks massive and it gives me a huge range! 8)

I've also installed some power plugs to let me charge the batteries without removing the top plate every time.

Sorry, no pictures yet. Iíll post them soon.

Itís the first time that Iíve used digital servos. Do they always make so much noise? Iíve also noticed that they start holding there position when power is applied. Is it possible to free the digital servos?


03-27-2009, 02:51 PM
A rover with one arm is goood ......

But how about a rover with two arms ..... and legs :P


03-27-2009, 07:17 PM
Ummm, wouldn't that belong in a different thread? Like, I don't know... bipeds? :tongue:

03-27-2009, 07:24 PM
I have a LM rover under the seat which would make it a hybrid.:wink:

Xan, how long till you get a video up of the sensor in action?

Sounds great.

03-28-2009, 03:16 PM

A rover with one arm is goood ......

But how about a rover with two arms ..... and legs :P
This is cheating!! :veryhappy:
Great looking bot. Or should I say botS! Nice paint job although the red white and blue in just 3 lines was enough. ;)

Xan, how long till you get a video up of the sensor in action? Sounds great.
No date yet, things always take out to be harder then expected. But give me a couple of weeks.

Here are some new pictures showing the new, bigger AL5D arm on the rover. The pressure sensor and IR with servo are already mounted. I have to wait for some parts to come in to get the IR mounted on top of the gripper. But the wire is already sticking out ;)

The AL5B didnít give me enough range to get over the IR sensor. No problem with the D version as you can see 8)


Here are some close-up photoís from the sensors.

Just some pics to compare the heights

Any comments are welcome!


03-28-2009, 04:10 PM
Very cool Xan :)

With that new force sensor, you could try showing off by carefully grabbing something delicate (like an egg). I'm looking forward to seeing what you do with it.

03-30-2009, 05:15 AM
That's a good idea with Easther comming up :)

04-01-2009, 03:51 PM
Nice pics Xan, very nice. looking forward to your progress with the mobile arm, I have a few parts ,but will need to concentrate on T1 first. keep up the good work and thank u for sharing this project with us.

04-02-2009, 04:55 AM
Hi 4mem8,

Thanks for your comments!

I have a few parts ,but will need to concentrate on T1 first.
Got a few parts..? Are you planning to join me on this one? ;)


07-18-2009, 01:16 AM
gr8 project dude and i jus wanna recomend u dat u can use a bigger gripper coz the gripper in the pic is looking small than to the robot arm and it would be helpfu l fr u to holda gr8 range of objects