6_wheeled robot

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I'm trying to control a 6-wheeled robot and I'd like to control each wheel independently. I've tried with skidsteercontroller (but I'm afraid that's only for 4 wheels) and with diffdrivecontroller (but the problem is that each pair of wheels works in the same way, and I want ALL the wheels to run independently...) Is there any other controller useful for my case? Or at least, is there any ros_package of a 6-wheeled robot example(similar for example to r-hex robot ?

I'm using ros indigo

Thanks a lot!!