Method for the recognition of a moving pedestrian
A method for the recognition of a moving pedestrian by means of a radar sensor system includes the steps of transmitting a primary radar signal into an observation space and of receiving a secondary radar signal reflected by the moving pedestrian. The secondary radar signal is processed, wherein the processing of the secondary radar signal includes the steps of generating a Micro-Doppler spectro-gram of the secondary radar signal, determining, based on the Micro-Doppler spectrogram, an observed bulk speed of the moving pedestrian, determining, based on the Micro-Doppler spectrogram, at least one gait cycle parameter of the moving pedestrian and determining, based on the determined observed bulk speed and the determined gait cycle parameter, an illumination angle between a moving direction of the moving pedestrian and the line of sight.
1. A method for the recognition of a moving pedestrian by means of a radar sensor system, wherein
transmitting a primary radar signal into an observation space; and
receiving a secondary radar signal reflected by the moving pedestrian; and
processing the secondary radar signal, wherein processing the secondary radar signal includes the steps:
(i) generating a Micro-Doppler spectrogram of the secondary radar signal;
(ii) determining, based on the Micro-Doppler spectrogram, an observed bulk speed of the moving pedestrian, wherein the observed bulk speed corresponds to a speed component that is related to the pedestrian's torso and is oriented along a line of sight extending from the moving pedestrian to the radar sensor system;
(iii) determining, based on the Micro-Doppler spectrogram, at least one gait cycle parameter of the moving pedestrian; and
(iv) determining, based on the determined observed bulk speed and the determined gait cycle parameter, an illumination angle between a moving direction of the moving pedestrian and the line of sight.
2. A method in accordance with claim 1 , wherein
the speed of the moving pedestrian in the moving direction is determined based on the determined observed bulk speed and the determined illumination angle using the formula v=vob/cos(θ), wherein v is the speed of the moving pedestrian in the moving direction, vob is the observed bulk speed and θ is the illumination angle.
3. A method in accordance with claim 1 , wherein
the Micro-Doppler spectrogram is generated by one of a Short-Time-Fourier-Transform and a Wigner-Ville-Distribution technique.
4. A method in accordance with claim 1 , wherein
the observed bulk speed is determined by means of a percentile-based method or a curve-fitting method.
5. A method in accordance with claim 1 , wherein
the at least one gait cycle parameter is an average duration of the pedestrian's gait cycle, an average gait cycle repetition frequency or a number of time bins related to one gait cycle.
6. A method in accordance with claim 1 , wherein
the at least one gait cycle parameter is determined by means of a Fourier analysis.
7. A method in accordance with claim 6 , wherein
a Fast Fourier Transform is applied to an upper envelope and/or to a lower envelope of the Micro-Doppler spectrogram to estimate the gait cycle repetition frequency.
8. A method in accordance with claim 1 , wherein
step (iv) includes relating the determined gait cycle parameter to the determined observed speed and to an estimated height of the moving pedestrian's thigh.
9. A method in accordance with claim 8 , wherein
a relation is used which is based on a kinematic human model.
10. A method in accordance with claim 8 , wherein
the height of the moving pedestrian's thigh is estimated based on a relationship between the height of the moving pedestrian's thigh and the overall height of the pedestrian, in particular based on the relationship Ht≈0.53·Hped, wherein Ht is the height of the moving pedestrian's thigh and Hped is the overall height of the pedestrian.
11. A method in accordance with claim 10 , wherein
the overall height of the moving pedestrian is estimated based on a statistical average height of pedestrians.
12. A method in accordance with claim 1 , wherein
in step (iv), the illumination angle is estimated by means of a recursive state estimator.
13. A system for the recognition of a moving pedestrian comprising:
a radar sensor system for transmitting a primary radar signal into an observation space and for receiving a secondary radar signal reflected by the moving pedestrian; and
an electronic processing device for processing the secondary radar signal, wherein
the electronic processing device is configured for carrying out a method in accordance with claim 1 .
14. A system in accordance with claim 13 , wherein
the radar sensor system is configured to be mounted at or in a motor vehicle.
15. A non-transitory computer program product including executable program code which, when executed, carries out a method in accordance with claim 1 .