Using Diverse Neural Networks for Safer Human Pose Estimation: Towards Making Neural Networks Know When They Don't Know

In recent years, human pose estimation has seen great improvements by the use of neural networks. However, these approaches are unsuitable for safety-critical applications such as human-robot interaction (HRI), as no guarantees are given whether a produced detection is correct or not and false detections with high confidence scores are produced on a regular basis. In this work, we propose a method to identify and eliminate false detections by comparing keypoint detections from different neural networks and assigning a 'Don't know' label in the case of a mismatch. Our approach is driven by the principle of software diversity, a technique recommended by the safety standard IEC 61508-7 [1] for dealing with software implementation faults. We evaluate our general concept on the MPII human pose dataset [2] using available ground truth data to calculate a suitable threshold for our keypoint comparison, reducing the number of false detections by approx. 61%. For the application at runtime, where no ground truth data is available, we introduce a method to calculate the needed threshold directly from keypoint detections. In further experiments, it was possible to reduce the number of false detections by approx. 75%. Eliminating keypoints by comparison also lowers the correct detection rate, which we maintained above 75% in all experiments. As this effect is limited and non-critical regarding safety we believe that the proposed approach can lead the way to a safe use of neural networks for human pose estimation in the future.