Motion Drive 3.0 - User Guide

Platform Configuration

(Click on Configuration - Platform Settings)

At the end of working through this section your platform will have its basic configuration and settings completed. This will be done in two phases, with the setting up of your sensors in between. Once both have been done, you will be ready to link your platform up with your simulation.

Setting up for Configuration

You should thoroughly check through your platform before commencing the configuration process, as it will involve the platform being driven, albeit in Manual Operation mode. Also, there is no point in finding the various settings for an empty unloaded platform. From this point onwards you should load your platform with between 50% and 70% of its design payload. That way the settings you establish will be useful and many will not need to be changed during operational runs.

You should not occupy the platform or cockpit, if mounted on the platform, during configuration - and indeed until you have satisfied yourself that all settings are well-tried. Better to control the platform and carry out the configuration from a safe position to one side. The platform load can be made up of some concrete blocks, for example. Whatever you do use to load up your platform, you must ensure that it is securely fixed to the platform and will not slide off or become dislodged.

Phase One - Axes etc.

Upon opening the platform settings page you will see this screen. For this first phase of configuration, you will concentrate on the top row of settings:- Axes, Drives, DAC Operation and Heave Sensors. Carry out the following configuration:-

Axes - Set to 2 for a two axis platform, set to 3 for a three axis platform.
Drives - enter the number of drives or motors you are using for your platform.
DAC Mode - set this to 1 for unipolar DACs and 2 for bipolar operation of the Classic Flight DAC. Set to 3 for a bipolar DAC that works using an MSB flag for negativity (see Some Basics).
Heave Sensors - you have a choice of using either 2 or 4 sensors for Heave (if applicable). See the relevant section on Heave sensors first before settings this value.

Once the values have been correctly set, then you need to click on Save Current. This will save the values you have entered, and they will be used on all future operations (unless you change them).

That is all you need to do for this phase. Now you should move on to set -up and calibrate your sensors if you have not already done so.

Phase Two - Drive Settings

Having set up the basic parts of your platform during phase one of this section, and then set-up your platform sensors, you are now ready to configure the drives and other basic elements of your platform.

For this phase you need to connect your DACs, motor control boards and motors and be able to drive them up and down.

Connecting your drives/motors.
Motion Drive 3.0 is very flexible in accommodating a wide variety of differing types of platform, but there have to be some fixed elements, otherwise the software would not know where to send which signals at which time. You have already seen some of these fixed elements when you were connecting downstream components to your USB modules earlier. Another fixed element is the layout and designation of your drives/motors. Below is a set of diagrams for all the possible drive layouts that Motion Drive can work with.

2 Axis - 2 Drive		2 Axis - 3 Drive		2 Axis - 3 Drive
front		front		front
2 Axis - 4 Drive		3 Axis - 3 Drive		3 Axis - 4 Drive
front		front		front

Having set up your drive layout in one of the above patterns, there are three other "fixed" elements that need to be ensured:-
1. For 3 Axis configurations, drives must be wired so that a positive signal to each drive moves the platform upwards at their location.
2. For 2 Axis configurations, drives A and C must be wired so that a positive signal to those drives moves the platform upwards at their location. Drives B and D (where applicable) must be wired so that a negative signal to those drives moves the platform upwards at their location. (ie A and C are wired in opposite to B and D)
3. If you are using four drives, drive D is configured using the settings for drive A.

Now that is done, you are ready to move onto the main drive settings. Scroll down the platform settings sheet and you will see a table of settings for the drives consisting of three settings for each drive. First, an explanation of the settings to be made.

PNRatio (Positive/Negative Ratio)
In most cases, a particular strength of drive signal will move the platform a greater amount downwards that it will upwards. This is because when moving downwards, the drive is helped by the weight of the platform and its payload, whereas moving upwards it has to lift that weight. So, in many cases you will need to input a stronger drive signal for an upward movement.
The PNRatio is a setting to compensate for that, so that a signal of the same strength will move the platform equally (roughly) whether it is driving upwards or downwards.

RAT (Relay Acceptance Threshold)
This applies where you are using motor control boards which use relay switches to turn the drive on or off. The RAT is the strength of signal which will just energise the relay (make it click in). This value is used when the platform is running but not active, so that the relays are held in their energised state - avoiding them clicking in and out which will wear out your relays more quickly.

MMT (Minimum Movement Threshold)
In most cases, there is a minimum signal which will make the platform move. This will be higher than the value used for the RAT, but still quite a low figure. The software applies this MMT value when the platform is moving so that the desired signal calculated by the software is translated into actual movement.

A Word about Signal Values
You will recall that the signals sent to the platform are in the format of an 8-bit binary word. Thus the value sent can be between 0 and 255. Added to that is the decision whether the signal is positive (driving the platfrom upwards) or negative (driving the platfrom downwards). So we have a range of -255 through to +255 for drive signals.
That works for unipolar DAC operation. For Bipolar we use one of the pins for the postive/negative flag, so the range is reduced to -127 to +127 for drive signals.

From now on, for setting up the drives and for manual operation, we will be talking in terms of the range of drive signal values:-
-255 to +255 for unipolar DAC operation
-127 to +127 for bipolar DAC operation.

For this next stage you need to have done the following:-
1. Connected the USB modules correctly to your downstream components including DACs, sensors, motors or drives.
2. Connected the USB modules to your PC, which should be switched on.
3. Opened Motion Drive 3.0 and be on the Platform Settings page.
4. Have your drives and other downstream components powered up.

Setting the RAT
This is the first setting to make. On the Platform Settings page set all relevant RAT values to zero. The click on Apply Current. Now go to the Manual Operations page and in the Select Drive Mode box, click on the radio button for Operate Drives Individually. For the first drive, say drive A, enter a low value (we suggest between one and five) in the Power box for that motor (all others should be zero). Enter a Duration time of say 1000ms. Then click on Drive platform. If you hear nothing, then the relay has not engaged. If you hear a click (you will need to listen carefully) then the relay has engaged and there will be a second click as it disengages at the end of the duration time.

If you did not hear a click, then you need to repeat the process having increased the value in the Power box by one each time. The RAT setting is the power value that you used when you first hear the relay engage. Record that power value and then reset the Power value for that drive to zero.

If you did hear a click, then you need to repeat the process having decreased the value in the Power box by one each time, until you first do not hear the click. The RAT setting you need is the Power value when you last heard the relay click to engage. Record that value and then reset the Power value for that drive to zero.

Repeat the process for each of the drives (remembering that for Drive D, your drive A values will automatically be used).

When you have found the RAT values for each drive that you are using, go back to the Platform settings page and enter those values into the RAT box for each drive. Then click on Save Current. You RAT settings will be saved and used each time you run the platform.

Note:
1. The allowable range for RAT settings is 0 to 20. If you dont hear the relay click before you reach a Power value of 20, then you need to adjust your motor control board so that the RAT is between zero and 20. You will need to see the instructions that came with your motor control board for information on how to do that.
2. If you do not have relays in your drive/motor control chain, then set the RATs to zero for each drive and click on Save Current.

Setting the MMT
This is the second setting to make. The process of setting the MMTs is exactly the same as for setting the RATs, except that instead of finding the point when the relays click, you are looking for the lowest Power value that moves the platform. Again, set the MMTs to zero for each drive and clikc on Apply Current.

Then using the Manual Operation, for each drive, gradually increase the Power setting (from a suggested start point of around 10) until you first see the platfrom actually move. This movement will be more of a twitch upwards than moving any distance. That Power setting is the MMT.

When you have the MMT for all drives, enter them into the Platform settings sheet and click on Save Current. Those settings will now be saved and used in future.

Note:-
1. As with the RATs, there is set allowable range for MMT settings. This is between 0 and 50. If you find that your MMT settings are turning out higher, then you need to make adjustment to your drive controller circuits.
2. The MMT is a separate figure to the RAT. The value you enter should be zero-based, not the incrment of power above the RAT value. (If your RAT is 7 and your MMT is 15 from actual trials, then you enter RAT as 7 and MMT as 15, not as 8 - 15 minus 7).

Setting the PNRatios
As mentioned above, the PNRatios are there to compensate for any difference in movement between upward and downward movements for the same strength of drive signal. The range of values allowable is between 50 and 200. A value of 100 is neutral - meaning no compensation is applied. Values below 100 compensate be apllying more power to downward movements that upward ones. Values above 100 compensate by boosting upward signal relative to downward signals - this is normally what is needed.
Start by setting the PNRatios to 100 and then click Apply Current.

Then go to the Manual Operation sheet and under Select Drive Mode, click on Operate Drives by Axes. The boxes for Power now refer to Roll, Pitch and Heave. The instructions that follwo will assume a 3 axis 3 drive platform, as that is the more complex to configure. For those with other types of platforms, the instructions remain the same except that you will be dealing with drive(s) that operate one axis only and, in the case of 2 axis platforms only dealing with Roll and Pitch.

It must be stated at this point that this process is one of trial and error, like setting the RATs and MMTs, but that you may not achieve perfect settings. The aim is to provide settings that improve the platforms performance as against the uncompensated situation. It is also an iterative process whereby having dealt with one Axis, you may have to revisit the settings after dealing with the next one.

Set up your platform so that it is level (use a spirit level to make sure).
You will deal with Roll first. Set a Power and Duration setting in the relevant boxes. We would suggest a relative modest setting of about 80 for Power and Duration such that you achieve a Roll of between 5 and 10 degrees. Click on Drive Platform. Now, keeping the same values, change the Power from plus to minus. Click on Drive Platform again. If the PNRatio is correct, then the platform should come back to level again. If it isn't level, then you need to work out from the resulting position whether the positive signal or negative signal needs to be boosted a little for each drive employed in a Roll. Try it both ways round too - starting with a negative Roll and returning to level with a positive one.

If the PNRatio needs to be changed, do the changes gradually. From the starting value of 100 (neutral) change by increments of 5 initially. Then when the change is too great, come back by increments of at a time. Likely values are between 105 and 115.
To make changes to the PNRatio, enter the new value in the relevant box and then click on Apply Current.

Having completed the PNRatios for the drives used in Roll, do the same for Pitch and finally for Heave. Remember that this is not an exact solution and some settings will be fine for one axis but not for another. That is ok, you need to find the "best fit" compromise settings for all the axes of your platform.

Once you have found the best PNRatios for your drives, enter them in the relevent boxes and click on Save Current. These values will now be applied to all future runs.

Note:-
1. Although the allowed values range from 50 to 200, if you are experiencing the need for values well away from 100 neutral, you should check the settings on your motor control boards as they may cause wide variations in motor performance.
2. PNRatios are applied to all drive situations except for "Operate Drives Individually" mode which applies no setting configurations whatsoever. So that mode is always available for basic testing and setting up.

In general, you will not change these drive settings once they have been established. You may find that either the PNRatio or the MMT may need slight alteration under loaded conditions.

Now you are ready to move on to Phase three.

Phase Three - Reset, Washout and Smoothing

This is the last phase of the platform settings (you'll be glad to hear). In this phase, you will set up the running configurations for Smoothing, Reset and Washout. Reset is the action when the platform can be sent through a routine to set itself level from any starting position. Washout is the routine during live running whereby the platform will subliminally return itself to level position when it has nothing else to do. Here we need to do some quick set-ups.

Reset Speed and Reset Boost
There are two settings here, the Reset Speed and the Reset Boost. The Reset Speed is just the power signal used consistently throughout the reset operation. The Reset Boost is an additional amount of power used to compensate for the platform going out of level during its routine. During reset, the platform will go through each axis in turn - roll then pitch then heave - setting itself level in each axis before moving on to the next. The boost is used to make an adjustment for the platform getting out of level in roll, whilst levelling itself in pitch or heave. Again this is a trial and error, but we can give you some guidance.

Having established your MMT values, that will give you an idea of what your reset speed should be. As a first try, set the reset speed as being the average of the MMT values. (The MMT is added to all drive signals during running operations, so an average MMT of 16 will be added to a Reset Speed of say 16 to give a total power signal of 32. ). Set the Reset Boost at 1. Then click on Apply Current.

Now go to the Manual Drive sheet and click on Reset Platform. (If the platform is already level, it won't move so dont worry - on such a case, use Manual Operation to drive the platform out of level position first). If the reset speed is a good choice, the platform should level itself in each axis - finally ending up level totally. (This assumes your sensors are working and calibrated correctly).

The overall effect should be a gentle and controlled sight. If the speed is too slow it may not reach level in each axis - if too fast it may go beyond level before stopping. Your aim is the minimum speed that the platform consistently finds level position. Remember, you might be sitting inside it at the time in future!! If you find that it goes out of level in roll, say, whilst levelling in pitch, then increase the Reset boost a little - see if that helps.

AS with the other settings, you need to enter your final value in the relevant box and click on Save Current to make it your default value.

Washout Speed and Washout Boost
The Washout Speed is the power signal sent to drives during Auto running to subliminally return the platform to level when it is not required to give a motion cue. The Washout Boost is applied when the platform is hard over in any axis, as it can sometimes need an extra boost of power to get the platform moving against the weight of cockpit and pilot.

As with most settings, this is a trial and error situation, and you may need to change the setting in the light of experience. At this point we are just interested in finding a rough starting position. As a rough guide, set the Washout Speed as being the Reset Speed x No Axes (assuming you found a nice gentle reset speed!). The Washout Boost should be set at about 10% of the Washout Speed.

Smoothing
You will be aware already that Motion Drive uses radial and axial accelerations in generating the motion cues for the platform. In some situations, these can be rather spikey and abrupt. So a facility has been included for smoothing these spikes and making the motion of the platform more continuous. Settings are provided for each axis separately. You will need to find the right settings for your platform through trial and error. The permissible value range is from 1 (no smoothing) to 99 (maximum smoothing).

You can't test these values yet (but not too long away), so just calculate them, enter them into the boxes on the Platform Settings sheet and click on Save Current.

WELL DONE! You have achieved a lot in completing this section, including the joy of seeing your platform moving under PC control. You have also gained a good insight into how your platform works and how to drive it manually.

Time to move on to establishing settings for games and planes.

© Active Simulation Limited 2007

Motion Drive 3.0 User Guide version 1.0