Obstacle detection on driverless industrial trucks

Status:

completed 12/1995

Aims:

Any driverless vehicle - from the small service robot used e.g. in hospitals to the industrial truck transporting heavy loads in the metal industry - must be equipped with an automatic obstacle detection system to avoid collisions with persons. For this purpose use is made of either mechanically actuated trip devices (bumpers) which buffer the kinetic energy once braking has been initiated or of electro-sensitive protective systems which detect persons prior to a collision and consequently cause the vehicle to brake. The project was aimed to define admissible forces allowed to occur in risk-free collisions and to determine assessment criteria for scanning obstacle detection systems.

Activities/Methods:

Force measurements (operating forces, force/time behaviour, final forces) were conducted on legs using numerous industrial trucks from the field with different types of bumpers (foamed material, Macrolon bows, metal plates). These measurements were intended to determine the actual "state of the art" and collect characteristic values of the breaking process (speed/time behaviour, path/time behaviour, deformation path). In connection with two non-contact sensor systems - one optical laser scanner and one ultrasonic system - it was possible to define assessment criteria for the "ability of detecting persons". Other aspects dealt with concerned the measurement uncertainty, the probability of detection, the protection against manual interference, the pollution monitoring, the failure detection and ageing monitoring, the dimensioning of the protective field and the PC configuration.

Results:

The dynamic forces measured on the bumpers reached peak values of 1000 N; maximum static values came to 800 N. In both cases peak forces exceeded the admissible uncritical limits. The non-contact prototypes turned out to be most suitable for flexible obstacle detection purposes on driverless industrial trucks. They allowed higher speeds, more narrow curves and differentiated vehicle reactions. Assessment bases were defined for both types of non-contact sensor systems. Use was made of the results in the context of European standardisation where they served to define limit values for collision forces and requirements for the design of non-contact collision protection systems.

Further informations:

Last Update: