Drive Controller Comparison
Chillout 1778 Driver Control Comparison
Taking a technical look at driver control.
In our development of Freezy Drive we took a look at existing drive controller in FRC. Here is a summary of some of those findings.
The default controller in FRC for many years has been the standard gaming joystick.
Axis Resolution: 127 steps
Pros:
- They are readily available.
- They are inexpensive
- They are ergonomic with well placed triggers and buttons.
- They have many buttons.
- They can also have a 3rd twist axis on the joystick
- Generally rugged construction, they will last for years.
Cons:
- Our tests show that the joysticks has only 127 steps across each axis extreme. This Is quite low and does not allow for fine control.
- Because of their large size they demand a lot movement between extremes. The need for the drive to move their complete arm to manipulate the joystick makes the motions clumsy compared to other controls. This can slow the ability to change the direction quickly.
- They must be mounted to a solid place on the drivers station. This limits the drivers movement to be able to see during the matches.
- The physical tension, centering and the feel of the joystick cannot be adjusted.
- They are difficult to transport because of the size and awkward shape.'
The Logitech F310 and Playstation controller are typical here.
Axis Resolution:
- Logitech Dual Action: 127 steps (no steps on triggers)
- Logitech F310: 256 steps (triggers 100 steps)
Pros:
- The joysticks support 256 (8-bit) steps across each axis. This is twice the resolution of the standard joystick. This is a noticeable improvement over the standard Joystick.
- Small portable controller, easy to transport.
- Ergonomic, easy to hold.
- Many drivers are familiar with the control.
- Many well places buttons and triggers.
- Well supported.
Cons:
- The joysticks are very small. This makes the fine control difficult. We see this in tests when position values can be noisy. The quality of the potentiometer pots is noisy at these resolutions.
- The physical tension, centering and the feel of the joystick cannot be adjusted.
The Xbox One series controllers are in a league of their own. Simple on the resolution of the joystick axis can these be considered a much more precise controller then other gamepads.
Axis Resolution:
- Xbox One: 800 steps
- Xbox One Elite: 1800 steps
- Triggers: 100 steps
Pros:
- The joysticks support 800/1800 (10/12-bit w/filtering) steps across each axis is amazing. This is approximately 10 times more resolution of the standard joystick. This is a noticeable improvement over the standard Joystick.
- Small portable controller, easy to transport.
- Ergonomic, easy to hold.
- Many drivers are familiar with the control.
- Many well places buttons and triggers.
- Joysticks length can be adjusted on Elite controllers.
- Well supported.
Cons:
- The joysticks are very small. This makes the fine control difficult. We see this in tests when position values can be noisy. The quality of the potentiometer pots is noisy at these resolutions.
- Centering is a little inconsistent. A deadzone is very important for centering.
- The physical tension, centering and the feel of the joystick cannot be adjusted.
At this time we have not tested a wheeled controller for resolution. The physical make-up of the controller has stopped us from using this style.
Axis Resolution: 256 steps
Pros:
- Can allow for smoother driving motion of the robot simply through the wheel itself negotiating the left and right turning. Less jerky then the to joystick tank drive.
- New drivers are familiar with these controls.
- Additional control buttons well placed
Cons:
- The size of the wheel and the need to actually turn it completely thru its radius makes slows down the ability for the driver to react and communicate large changes to the robot.
- The accelerator is separate, demanding a foot or taking a hand off the controller to control speed. Reducing to one had driving.
- Needs a permanent fixed base, limiting the drivers ability to move around to see the field.
- Difficult to transport, large.
This is controller style we used for Freezy Drive 1.0. Generally we are happy with them and it is a good place to start. We use the Realflight Interlink and the Realflight Elite Interlink Controller. There are many similar inexpensive USB controller available on EBAY for less the $80. The cons are more detailed here because of our experiences during competition.
Axis Resolution: 256 steps
Pros:
- The joysticks support 256 (8-bit) steps across each axis. This is twice the resolution of the standard joystick. This is a noticeable improvement over the standard Joystick.
- Joysticks are longer then a gamepad and allow for much higher precision. Our tests show the easy repeatability and control even at the higher resolution. The gimbals are not noisy.
- Small portable controller, easy to transport.
- Ergonomic, easy to hold.
- The sticks allow for thumb control or pinch style control, with helpful grip treatment in those areas.
- Many drivers are familiar with the controller, especially if they have flown quadcopters or RC airplanes.
- Many buttons and triggers.
- Well supported in Windows as a joystick.
Cons:
- The quality of construction is low. With the rigors of competition we had to repair some parts. Most of the gimbal parts are plastic. The last controller we got did have metal pins for some of the smaller axles.
- Replacement parts are not available for these inexpensive controllers. WE had to laser cut new centering. Any customization we needed to fabricate.
- Limited spring tension adjustment with different springs, but the centering and the feel of the joystick cannot be adjusted.
- Button style may need to be changes. We used push buttons and needed more momentary switches beyond the standard toggles.
- The USB cable is fragile. With Freezy Drive 1 we replaced the cable with a more rugged cable.
- The sticks need to be protected for transport and storage. There are many inexpensive carrying cases available.
A typical and very popular example of this controller is the FrSky Taranis X9D Plus. This is probably the most popular controller among quadcopter pilots. There is a strong community supporting this controller. There are also many mods that can be done to this radio. The controller runs the open source software OpenTX. Through the software all transmissions can be disabled.
This controller runs an STM32 chip. There is a real potential here to modify the OpenTX software to coordinate with the drivers station to use the built in display, speaker and the vibration to create an incredible FIRST specific controller. This is beyond the expertise of our team at this time. But we will look into it.
Axis Resolution: 256 steps
Pros:
- The joysticks support 256 (8-bit) steps across each axis. This is twice the resolution of the standard joystick. This is a noticeable improvement over the standard Joystick.
- Joysticks are adjustable in many many ways. Length, tip style, spring tension (infinite) and overall tension to rotation. Each individual axis can be customized in this way. So the feel of a gimbal in the horizontal axis may be adjusted independently of its vertical axis.
- Our tests show the easy repeatability and control even at the higher resolution. The gimbals are very nice.
- The quality of construction is better. The gimbals have many metal parts to add to the ruggedness and smoothness of the controller.
- Small portable controller, easy to transport.
- Ergonomic, easy to hold.
- The sticks allow for thumb control or pinch style control, with helpful grip treatment in those areas. There are many custom tips available.
- Replacement parts are readily available for these controllers. There are a lot of customized parts available for this popular controller.
- Many drivers are familiar with the controller, especially if they have flown quadcopters or RC airplanes.
- Many buttons and triggers.
- Well supported in Windows as a joystick.
Cons:
- Button style may need to be changes. We used push buttons and needed more momentary switches beyond the standard toggles.
- The USB cable connector is on the back. It is a fragile placement.
Through our experiments with this, we have discovered ways to get a controller with better construction and higher resolutions. TO do this requires new electronics in the controllers. We are currently looking to increase the resolution of the gimbals on a Taranis controller to 2500 steps across the axis range at a rate of 1000hz. At these resolutions we can also implement a filter to further smooth the motion of the sticks.
Most gimbals use a potentiometer on each axis. These can, over time degraded in centering and accuracy. The new Freezy Drive controller will have hall effect sensors allowing for a much longer life do to the non-contact of hall effects.
Freezy Drive 2.0 is an ongoing project, but to date the prototypes look hopeful.