[jspatz1]

Everyone should take note that it helps the helpers help you when you explain your problem this thoroughly. Length of description is not a problem.

First of all, as far as I am aware there are no restrictions on using flow controls and metering valves. You can use as many COTS commercial flow controls you want as long as they are unaltered and meet the pressure requirement. You certainly want to use them on both directions of your actuator. There are clever ways to use flow controls in nested or sequential ways to achieve the flow pattern you want.

My philosophy on pneumatic actions such as this is that pneumatic acuatation is only what it is, a somewhat spongy push or pull with no live speed or force control. If it does not give you the behavior you want, you need to change what is being actuated so that it does. With the restrictions FRC puts on us (no 3-position valves, no servo-valves, no servo-regulators) you do not really have the means to control your pneumatics to match the task, so you must design the task to match the pneumatics.

I am refering to using counterweight, springs, friction, weight distribution, and shock absorbers to even your load through its travel, so your actuator yields a uniform result. It is better to design your mechanism so that it utilizes the uniform speed/force that pneumatics inherently provide, than to use complex flow control methods to try to make the pneumatics into something they are not. It is the same idea as balancing the load on motors to give a more uniform result.

We had a very similar situation this year, as did many teams, where we were pneumatically lifting our gripper from the floor to the scoring position. Obviously the same force that you need to lift the dead weight of the arm from the floor is more than you want to have at the top of the stroke. We simply found with experimentation the right length and strength of springs (or elastics) to assist the lift, so that there was prompt motion at the bottom, uniform speed throughout, and a relatively soft landing at the top. Counterbalancing your load this way may even require a negative load at the bottom (air cylinder is actually pushing the arm down to the low position) in order to get the uniform result. A spring assited lift will allow you to turn down the speed control and still get prompt motion. You can also put springs on shock cords so that they balance only a portion of the stroke, such as a spring assist at the bottom, nothing in the middle, and spring resistance at the top. Perhaps one spring or elastic can be centrally positioned to do both jobs. If you have some weight allowance left, counterweighing your arm to balance the load is a possibility. Gas springs are available and allowed to balance the load. Although I do not usually like friction methods, creating a friction source at the top of the stroke to help decelerate the load is an option. Gas shock absorbers are available to help decelerate the end of stroke. Air cylinders are available that have adjustable shock asborbtion built into the cylinder itself. The point is, some combination of balancing methods will yield the uniform motion you want, and then you can adjust the speed to suit. It takes experimentation.

Of course there are tricks you can do with flow control, such as having the arm motion physically switch a manual diverter valve from one flow control to another near the top of the stroke, or having a microswitch in the stroke switch a valve or clutch. But such tricks can be prone to adjustment, and add complexity to your system. Simply changing the nature of the load to give the desired result is the simplest and most reliable approach.