Hey all,

I'm an Electrical Engineering student undertaking an Advanced Control subject. I need to design a sliding mode controller for a gantry crane that limits the swing angle to say, less than 15 degrees while the suspended load is moved across the gantry beam. I was wondering if anyone could give me a few pointers. I have already successfully designed and implemented a pole placement controller but I am having a lot of trouble getting my head around practically designing a sliding mode controller.

The crane is a single input two output system, the dynamics equations are,
x(s) = 5.8/(s(s+2.4)
Theta(s) = -5/((s+2.4)(s^2 +7.8))

If anyone is willing to help and need more info my email is [email protected].

Thanks in advance.
Andrew

 

> I'm an Electrical Engineering student undertaking an Advanced Control subject.
> I need to design a sliding mode controller for a gantry crane that
> limits the swing angle to say, less than 15 degrees while the suspended load is
> moved across the gantry beam.

Limiting the sway is going to be a function of limiting the acceleration of the motor system x(s). That limit can be determined if you look at the equation for a swinging pendulum.. Usually people are more interesting in reaching the final position without the load swinging at all. There are algorithms for this but they require a long convolution filter with the period of the swinging.

> I was wondering if anyone could give me a few pointers. I have already successfully
> designed and implemented a pole placement controller but I am having a
> lot of trouble getting my head around practically designing a sliding mode controller.

Sliding mode controllers are easy. If it looks difficult you are doing something wrong. Optimizing the performance may take some effort.

> The crane is a single input two output system, the dynamics equations are,
> x(s) = 5.8/(s(s+2.4)
> Theta(s) = -5/((s+2.4)(s^2 +7.8))

Do you use something like Mathcad, Matlab, Scilab etc?

These pdf files may help for starters
http://deltamotion.com/peter/Mathcad/SMC/