Quick Start Guide

On this page, I (OlliW) will briefly describe the initial steps which are required to set up the STorM32-BGC to function correctly.

Ultra-Quick Start Guide:

• Use the "Calibrate Acc" tab to calibrate the imus.
• Use the "Configure Gimbal Tool" to set the Imu1 Orientation, Imu2 Orientation, and Motor Pole parameters correctly, and to set the Motor Direction parameters to "auto".
• Use the "Get Current Motor Directions" option to set the Motor Direction parameters.
• Use the "Get Current Pitch and Roll Motor Positions" option to set the Startup Motor Pos parameters for pitch and roll.
• Use the "Adjust Yaw Startup Motor Pos Parameter Tool" to align the yaw axis to point forward at startup.

Below a somewhat less quick "Quick Start Guide" follows. It tells you what you need to know and what to do.

Supported Gimbals

The STorM32 controller can currently be used for the following setups:

• 3-Axis with single Camera IMU: Only one IMU, connected to the I2C port and mounted to the camera, is used.
• 3-Axis with Camera & on-board IMU: In addition to the camera IMU the StorM32 on-board IMU is used as a 2nd IMU. The StorM32 board must be mounted on the gimbal above the yaw motor.
• 3-Axis with Camera & separate 2nd IMU: In addition to the camera IMU a further IMU connected to the I2C#2 port is used as 2nd IMU. The board can be mounted anywhere, but the 2nd IMU must be mounted on the gimbal above the yaw motor.
• 2-Axis: This is not "officially" supported but users figured out that the controller can be set up to work fine with a 2-axis gimbal. Only one Camera IMU is attached to the I2C port. The 2nd IMU is not supported in this configuration.

Both the 3-axis and 2-axis gimbals with single IMU are obviously easier to set up since one doesn't need to be concerned about the 2nd IMU and what's required to get it working correctly. The following focuses on the 3-axis dual-IMU setups.

Preparation

Things to know before starting:

• Comprehend the Dos and Dont's.
• Understand the importance of a proper gimbal mechanics, read The Gimbal and especially Balancing the Gimbal!
• Get familiar with the board, inspect the Pins and Connectors.
• Use the latest firmware and GUI. To download the latest firmware package see Downloads. To flash the firmware to the board see How to flash firmware. Read the updates and installation instructions in the respective posts at the rcgroups thread, also check these posts for known bugs.
• Check that your setup matches one of the supported setups mentioned previously.
• Understand the "Read", "Write", and "Write+Store" mechanism in the GUI.

Finally, good advice:- Please take any recommendations from these links seriously!

Calibration

The accelerometers of the IMU modules need to be calibrated for optimal performance (the gyros too, but that's beyond reach). Several calibration techniques are known, and two of them are implemented in the STorM32 project, called 1-point and 6-point calibration.

Unfortunately, it is not finally clear what method is the best. This is because not much useful info is in the web and I don't have the resources for an extensive research project on this, but this is what would be needed. Hence, the situation is currently a bit experimental and might appear fuzzy to many users, but - to also have a good message - the knowledge and experience increases and calibration procedures might improve with time.

The reasons for a calibration are different for the camera and the 2nd IMU.

Camera IMU: The calibration mainly affects the "horizont drift", i.e. the accuracy with which the horizont is hold in quick yaw turns and other high-g maneuvers. It also determines the accuracy of how well the camera is level, but this could in principle be tuned out easily by other means (e.g. offset parameters). The main concern is the performance in high-g maneuvers.

Second IMU: The measurement accuracy of the 2nd IMU is by itself not very important, it is however very important that the 2nd IMU data is consistent with the camera IMU, and it is the more important the higher the number of motor poles is.

Some insights have been made so far.

Imu Orientation: As a general trend, the z axis is much more wrong than the x and y axes.

Calibration Accuracy: A 6-point calibration is meaningful only if it is done very accurately. A poorly undertaken 6-point calibration can easily result in a poorer performance than a supposedly "lesser" 1-point calibration. The quality factor can give an indication.

From that these rule of thumbs follow:

Rules of thumb:

• The calibration only needs to be as good as you need it to be. If you are happy with how your gimbal works, you don't have to spend time on a (better) calibration.
• IMU orientations with the z-axis up or down seem preferable, as it lessens the need of a calibration. But don't get fooled here, equally good results can be obtained for any orientation. Some of the best videos out there were in fact recorded with the IMU's z axis horizontal. It just means that with the z axis up or down it's more likely to get away with a lesser calibration for a desired level of performance.
• The calibration of the camera IMU is more important than for the 2nd IMU, i.e. for the 2nd IMU a "lesser" calibration might be fully sufficient.
• The calibration of the 2nd IMU is the more important the higher the motor pole count is.

Even though, for the reasons mentioned before, a clear cut calibration recipe cannot be offered currently, some recommendations seems at place:

Current Recommendations:

• A 1-point calibration is fairly simple, and is hence recommended for both the camera and 2nd IMU.
• If possible choose IMU orientations with the z-axis up or down, but that's no must as explained before.
• Don't do a 6-point calibration if you don't plan to do it really accurately (check out the rcgroups thread).
• If motors with 12 or 14 poles are used, a 1-point calibration of the 2nd IMU is most likely sufficient. High-pole motors require in contrast a careful 2nd IMU calibration.

Video Calibration Tutorial: Rcgroups user mackar did a great video on the 6-point calibration. Go to 6-Point Calibration.

Finally, this important advice:

Safe your calibration data to a file! 

Ideally safe it from within the Calibration dialog, as this stores the most detailed information. Consider also to post your calibration files in the rcgroups thread, so that I and others can enhance our knowledge and hopefully develop better calibration schemes.

Basic Controller Configuration

The algorithms used in the STorM32 controller need to know some aspects of your gimbal in order to work correctly. If any of this information is incorrect, the controller will misbehave. Unfortunately, an incorrect setup will not always immediately reveal itself, but will lead to misbehavior at a later stage, e.g. when a new function is activated, and therefore you might not associate it with the earlier faulty setup. So, please accept the following statement:

Just because a setting seems to work correctly doesn't mean that it is correct!

One implication is that adjusting the fundamental parameters by trial-and-error is the best approach in producing all sorts of non-obvious problems. Fortunately, a straight-forward setup procedure is available and if followed, guarantees correct settings. So, the above could be rephrased also as "Don't try to be smart, just follow the recipe". That's in fact the best advice possible here.

The parameters we are talking about are contained under the "Gimbal Configuration" tab in the GUI:

• Imu1 Orientation
• Imu2 Orientation
• Motor Poles
• Motor Directions
• Motor Startup Positions

Some of them should be adjusted before the motors are activated, some can only be adjusted with the motors enabled.

Before the motors are enabled for the first time

The Imu-1 and Imu-2 orientations and number of motor poles should be adjusted before the motors are activated, and the motor direction settings, initially set to "auto" in order to find correct rotation directiony.

This is most easily done by using the "Configure Gimbal Tool" (accessible under the "Gimbal Configuration" tab in the GUI), which is started by clicking on the respective button. Just follow the instructions step by step:

• It will guide you through a simple procedure which determines the Imu1 and Imu2 Orientation parameters.
• It then will ask you to enter the number of poles of your motors. The number of poles for your motor should be available in the motor data sheets. For instance, a 12N14P motor has 14 poles. The number of poles corresponds to the number of magnets, which you can see on the inner side of the motor bell. So, if in doubt you can easily determine the number of poles by simply counting the magnets.
• Finally, as mentioned above, the Motor Direction parameters are set to "auto".

After motors have been enabled for the first time

With the Imu-1 and Imu-2 orientations, and motor poles set correctly, and the motor directions set to "auto", one can enable the motors (all motors!) and start the gimbal. The controller should go through the initialization steps and level the camera (green led blinks), and then reach the "Normal" state (green led continuously On). Note: You can see what is happening by initiating and starting the "Data Display". Once the "Normal" state is reached the Motor Direction and the Startup Motor Pos parameters can be set using the "Tools" menu:

• Go to the "Tools" menu and execute the "Get Current Motor Directions" option. This will copy the auto determined motor directions into the Motor Direction fields.
• Go to the "Tools" menu and execute the "Get Current Pitch and Roll Motor Positions" option. This will copy the current pitch and roll motor positions into the Pitch and Roll Startup Motor Pos parameter fields.
• Go to the "Tools" menu and execute the "Adjust Yaw Startup Motor Pos Parameter Tool". This opens a dialog box which allows you to align the yaw axis such that the camera points to the forward position. Don't worry that the alignment being undone when closing the dialog box, this is normal.

The adjustments made in these steps become effective only at the next startup of the gimbal.

The Next Steps

The next steps are to tune the PID parameters. It is not part of this Quick Guide, since the PID values are not fundamental for the controller to work correctly; they are (very) important for the performance. Once tuned, one can start to enjoy all the great and partly unique possibilities of the STorM32 controller. :)