# Critical VIO Instability and Calibration Failure on Stinger (D0013) with Brand New VOXL 2 Mini

Source: https://forum.modalai.com/topic/4929/critical-vio-instability-and-calibration-failure-on-stinger-d0013-with-brand-new-voxl-2-mini
Category: General Questions (https://forum.modalai.com/category/2/general-questions)
Posted: 2025-12-16 11:26:57 UTC by YUUJI INOUE
Replies: 3 · Views: 541

## YUUJI INOUE · 2025-12-16 11:26:57 UTC

Dear ModalAI Support Team,

I am writing to report a critical issue with my Stinger drone (SKU: MRB-D0013). I have recently installed a brand new VOXL 2 Mini flight controller on this unit. Despite extensive troubleshooting, including resetting to factory defaults and comparing with a working Starling 2 (D0014), the VIO system fails to initialize correctly and diverges immediately.

We suspect a hardware defect related to the IMU orientation, camera focus/calibration, or an incompatibility with the default configuration for this specific unit.

### Issue Summary
- **Symptom**: VIO (both QVIO and OpenVINS) diverges immediately or reports "BAD_CAM_CAL".
- **Observation**:
    - In VOXL Portal, the VIO overlay shows the drone's estimated position diverging.
    - When manually moving the drone, the VIO estimated motion is often inverted (e.g., pitching up is interpreted as pitching down) or axes are swapped, even with default extrinsics.
    - `voxl-qvio-server` reports `BAD_CAM_CAL` and `NOT_STATIONARY` errors.
    - `voxl-calibrate-camera` fails for both `tracking_front` and `tracking_down` with high re-projection errors (> 0.9), citing "motion blur" even in a well-lit, static environment.

### Troubleshooting Steps Taken
1.  **Factory Reset**:
    - Ran `voxl-configure-mpa` (factory reset).
    - Ran `voxl-configure-extrinsics D0013_Stinger` (reset to default D0013 extrinsics).
    - Ran `voxl-configure-cameras 22` (reset to default Stinger Dual AR0144 config).
    - Result: VIO still diverges with `BAD_CAM_CAL`.

2.  **IMU Data Analysis**:
    - Analyzed `voxl-inspect-imu imu_apps` raw data (with `rotate_common_frame: false` and `true`).
    - The IMU data suggests the physical orientation might be different from what the default configuration expects (Roll 180 + Yaw 180 vs just Roll 180), or the driver correction is not applying as intended for this specific unit.
    - Even when manually adjusting `extrinsics.conf` to match the observed IMU orientation (FLU) and Camera orientation (FRD), VIO stability could not be achieved.

3.  **Comparison with Starling 2 (D0014)**:
    - We have a working Starling 2 unit. Applying Starling 2's configuration to Stinger (as a test) also resulted in divergence, confirming the hardware configuration is indeed different or defective.

4.  **Camera Calibration**:
    - Attempted `voxl-calibrate-camera` for both cameras.
    - Consistently fails with high re-projection error, suggesting potential lens focus issues or sensor alignment problems.

### Request
Since we are using a brand new VOXL 2 Mini board, we want to ensure there are no configuration mismatches or firmware issues. However, given that it fails to operate with factory default settings and cannot be calibrated, we are concerned about a potential initial defect in the sensor modules or the board itself.

Please review the attached diagnostic logs (`diagnostic_logs.txt`) and advise on the next steps for troubleshooting.

### Attached Files
- `diagnostic_logs.txt`: Output of `voxl-inspect-sku`, `voxl-version`, `voxl-inspect-services`, `voxl-inspect-extrinsics`, and `voxl-camera-server.conf`.

Thank you for your assistance.
[diagnostic_logs.txt](https://drive.google.com/file/d/1K95G4X17biGRex4oK3h-eWsSrEj8g1mX/view?usp=sharing)

## Reply by zauberflote1 (ModalAI staff) · 2025-12-16 19:49:15 UTC

@YUUJI-INOUE 
Please update your SDK version.

Regarding your rotation concern, on D0013 the board the is mounted upside down, but the common frame assumes the board is mounted in the default orientation. For instance, consider the rotation listed in the following file for imu_apps and body
```
/etc/modalai/extrinsics.conf
```
If you transform IMU samples by the SE(3) trafo, you'll see they will align with FLU coordinate frame. A quick sanity test would be to check a static IMU sample with inspect-imu and rotate it by the above-mentioned trafo. I should also add that on our soon-to-be-released SDK 1.6.3, we included some flavours of IMU pipes, including body frame, etc. You should be able to access this [here](https://gitlab.com/voxl-public/voxl-sdk/services/qrb5165-imu-server/-/tree/dev?ref_type=heads), in case you wish to build it on your own.

In regards to VIO, the latest [OV-server](https://gitlab.com/voxl-public/voxl-sdk/services/voxl-open-vins-server/-/tree/dev?ref_type=heads) is significantly better than previous versions. Additionally, if you load the latest imu-server and OV server, you should get all estimates in body frame wrt. {G}. PS: All extrinsics are corrected internally, so you don't need to manually edit the .conf files.

## Reply by YUUJI INOUE · 2025-12-17 15:57:42 UTC (in reply to zauberflote1)

@zauberflote1 
The problem was solved after upgrading to SDK1.6.2, thank you.

## Reply by YUUJI INOUE · 2025-12-17 23:50:52 UTC (in reply to YUUJI INOUE)

@YUUJI-INOUE 
This is the setup I did for stable operation, please let me know if there are any mistakes.

# Stinger (VOXL 2 Mini) VIO Setup Guide

This document provides instructions for setting up a stable VIO (Visual Inertial Odometry) environment on the ModalAI Stinger (equipped with VOXL 2 Mini).
It focuses on SDK version selection and correct configuration commands for the D0013 build to ensure reliable autonomous flight.

## 1. Prerequisites

*   **Drone**: ModalAI Stinger (VOXL 2 Mini)
*   **Configuration ID**: D0013 (Stinger V2)
*   **PC Environment**: Linux/Ubuntu with ADB (Android Debug Bridge) installed
*   **Network**: Internet connection required for the drone (via Wi-Fi) for `apt-get` operations

## 2. SDK Version Check and Installation

**IMPORTANT**: Development versions (Alpha/Beta) of the SDK may cause unstable VIO behavior. It is **strongly recommended to use the Stable SDK 1.6.2**.

### 2.1 Check Current Version
Connect to VOXL via ADB and check the version:
```bash
adb shell voxl-version
# OR
adb shell apt-cache policy voxl-suite
```
If you see versions like `1.6.3~alpha`, you must downgrade.

### 2.2 Install SDK 1.6.2
Force install the stable version:

```bash
# Run inside VOXL shell or via adb shell
adb shell "DEBIAN_FRONTEND=noninteractive apt-get install -y voxl-suite=1.6.2"
```

### 2.3 Install Required Libraries
To fix dependency issues with OpenVINS in SDK 1.6.2, install the `voxl-ceres-solver` library (`libceres.so.2`):

```bash
adb shell "apt-get install -y voxl-ceres-solver"
```
*Note: Without this, `voxl-open-vins-server` will fail to start.*

## 3. Factory Reset and Configuration

Apply the correct presets for Stinger (D0013). Using these commands is more reliable than manual configuration.

### 3.1 Configure Extrinsics
Load the camera and IMU geometry for Stinger V2 (D0013).

```bash
adb shell "voxl-configure-extrinsics D0013_Stinger_V2"
```

### 3.2 Configure Vision Hub
Configure how VIO data is sent to PX4 using the Stinger-specific preset.

```bash
adb shell "voxl-configure-vision-hub factory_enable_vfc_pos_back_flow_d0013"
```

### 3.3 Configure OpenVINS
Reset the VIO server configuration.

```bash
adb shell "voxl-configure-open-vins factory_enable"
```

### 3.4 Configure PX4 Parameters
Load optimized PID gains and flight parameters for Stinger (D0013).

```bash
adb shell "voxl-configure-px4-params -n -p MRB-D0013"
```

### 3.5 Enable VIO (Official Helper)
Load the official parameter helper file for indoor VIO flight without GPS.

```bash
adb shell "voxl-configure-px4-params -n -f /usr/share/modalai/px4_params/v1.14/EKF2_helpers/indoor_vio_missing_gps.params"
```

### 3.6 Configure ESCs
Upload Stinger-specific ESC parameters.

```bash
adb shell "/usr/bin/voxl-esc setup_d0013"
```
*If you encounter `invalid option` errors, use the manual python script method:*
```bash
adb shell "systemctl stop voxl-px4 && cd /usr/share/modalai/voxl-esc-tools/ && python3 voxl-esc-upload-params.py --params-file ../voxl-esc-params/D0013/lumenier_2305_2400kv_GF_D90_4S.xml && systemctl start voxl-px4"
```

### 3.7 Change ESC Mode (Critical)
Change ESC control from RPM mode (default) to Power mode to ensure reliable motor startup.

```bash
adb shell "px4-param set VOXL_ESC_MODE 0"
```

### 3.8 Motor Test
**WARNING: REMOVE PROPELLERS BEFORE TESTING**

Spin Motor 0 (Front Right) for 2 seconds to verify ESC communication.

```bash
adb shell "systemctl stop voxl-px4"
adb shell "cd /usr/share/modalai/voxl-esc-tools/ && python3 voxl-esc-spin.py --id 0 --power 15 --timeout 2 --skip-prompt True"
adb shell "systemctl start voxl-px4"
```

## 4. Advanced Optimization (Critical for Stability)

### 4.1 OpenVINS Optimization (Stinger Specific)
To prevent data corruption and initialization errors on Stinger (D0013):
1. Disable `imu_body_frame_mode`.
2. Change configuration folder to `fpv`.

```bash
adb shell "sed -i 's/\"imu_body_frame_mode\":\ttrue/\"imu_body_frame_mode\":\tfalse/' /etc/modalai/voxl-open-vins-server.conf"
adb shell "sed -i 's/starling2/fpv/g' /etc/modalai/voxl-open-vins-server.conf"
```

### 4.2 Stabilize Connection After Reboot
Prevent `voxl-vision-hub` from starting before `voxl-open-vins-server` is ready by adding a 10-second delay.

Edit `/etc/systemd/system/voxl-vision-hub.service`:

```bash
adb shell "sed -i 's/After=voxl-wait-for-fs.service/After=voxl-wait-for-fs.service voxl-open-vins-server.service/' /etc/systemd/system/voxl-vision-hub.service"
adb shell "sed -i '/ExecStart=\/usr\/bin\/voxl-vision-hub/i ExecStartPre=\/bin\/sleep 10' /etc/systemd/system/voxl-vision-hub.service"
```

### 4.3 IMU Calibration
If VIO is unstable or the Web Portal Health Check shows "IMU Calibration Missing", perform calibration:

```bash
adb shell "voxl-calibrate-imu"
```
Follow the on-screen instructions to place the drone in 6 orientations.

## 5. Apply Changes and Reboot

After applying all settings, reboot the drone. **A hard power cycle (unplug battery) is recommended** to ensure all sensors reset correctly.

```bash
adb shell reboot
```

## 6. Verification

### 6.1 Check Services
```bash
adb shell voxl-inspect-services
```
Ensure `voxl-open-vins-server`, `voxl-vision-hub`, and `voxl-px4` are **Running**.

### 6.2 Check VIO in VOXL Portal
Access the VOXL Portal (via IP address) and check the **VIO (3D View)**:
*   **Orientation**: Does the drone in the view verify Pitch/Roll/Yaw movements correctly?
*   **Position**: Does the drone stay still in the view when the physical drone is stationary? (No drifting/divergence)

### 6.3 Check QGroundControl (QGC)
1.  **Local Position**: Is the drone icon visible on the map?
2.  **Position Mode**: Switch flight mode to **Position**. It should say "Ready to fly" or "Position mode enabled" (not "Rejected").
    *   If you can enter Position mode without GPS, VIO is working.

## 7. Operational Best Practices

1.  **Power On**: After plugging in the battery, **leave the drone static on a level surface for ~30 seconds**. This allows the gyro to calibrate biases and services to start.
2.  **Initialize VIO**: Pick up the drone and move it in a **large figure-8 motion** to excite the IMU and cameras.
3.  **Pre-flight Check**: Do not take off until you can successfully switch to **Position** mode in QGC.
    *   *Note: If initialization fails (rarely), perform a reboot.*

## 8. Troubleshooting

**Q. Cannot enter Position Mode on the ground ("Not Ready")**
A. Check the following:
1. Run `voxl-inspect-pose vvhub_body_wrt_local` to see if VIO data is streaming.
2. If no data, perform a hard reboot (battery pull) to fix timestamp sync issues.
3. Set `en_voa` to `false` in `voxl-vision-hub.conf` to disable obstacle avoidance (can cause extrinsics errors).
4. Ensure `vio_pipe` is set to `ov`.