i need some good advice, not even sure im in the right place

hi everyone, recently been looking in to moifying a peice of manually operated equiptment i have and making it electricly operated. i have no idea where to start of what methods i need to get a grasp of. the basic outline is that i have seveal speed sensors, weigh cells and servos and i want to design some sort of program to process the information from the speed sensors ect and ouutput the relevent signals to the servos ect. im reliably informed that this sort of software is possible to create but my major issue is how do i convert the signals coming out of the computer port in to electrical current to activate the electrial appliances?

and advice would be much apreciated

thanks in advance

S Shepherd