I want to build a linear actuator which can (with some precision) have a displacement of around 70~80 cm ,the load on the linear actuator will be around 10~15 Kg(the load will be a rod about 2 mtrs long, the other end of which will be again on a similar actuator). Some other features that i would need are: the actuator should not have back driving characteristics i.e. it should be self locking. Also suppose the actuator is moving in the vertical direction(i.e. up-down) then there if my linear actuator is not moving then the other end of rod should be able to move up-down by a small amount i.e. if vertical is Z-axis then the rod should be able to make an angle ~20 degrees with the Z-axis.
So i was thinking (after looking on net/forum) that using a screw-nut(acme screw) arrangement seems easy to implement and control ?
Since i don't know an iota of mechanical design except common-sense
so easy of construction is a major requirement!!!
If we use an acme screw with efficiency < 35% we can prevent back-driving. but about the 2nd requirement i am not sure. will the second requirement introduce some backlash in the gear?
Also i was initially thinking about using a geared DC motor with encoders , then what kind of precision can i expect ? or using maybe a stepper would be a good idea?
How do i calculate the torque needed for a motor to move such a load ?
My preference of screw-nut gear was due to my thinking that i can get this build easily in a turning shop ( that has a lathe and some drills and some other things.) , since i am not from mechanical background , so i need to know about things like what kind of material would be suitable for screw and nut in my case and what possible things might go wrong
Also this whole linear actuator assembly will be quite long , so how to minimize the effects like vibrations of robot movement,bending of screw ?
How should i best support the long screw , means i need to attach it to the robot chassis , so i need to attach the screw at top as well as bottom.