DE8700063U1 - Optoelectronic protection zone device - Google Patents

Description

til (ti · · «

Ii ( ( '' te tti ti ·

State of the art;

A wide variety of warning devices are used to protect dangerous machines, but there are still areas that have hardly been or poorly protected. The sensors used so far include:

Light curtains, microwave radar, microwave Doppler, ultrasonic echo measuring systems, passive infrared sensors, contact mats, time-of-flight distance measurements, etc.

Each of the systems mentioned has certain disadvantages when used in a specific application.

Light curtains are limited in their use by the reflectors required on the opposite side.

Microwave time of flight measurements are quite complex and do not offer the necessary resolution in the close range. Doppler systems cannot detect distances. Light time of flight distance measurements are quite complex.

Ultrasonic echo measuring systems depend on the travel time of the sound and therefore have a relatively long reaction time. In addition, they have a very wide measuring beam, which prohibits measurements in confined spaces.

Other systems proposed so far have light pulses that operate statically in a solid angle range; these systems are .

I · t * I I

■ are often complex and do not have the option of adapting flexibly to changing monitoring areas. The system with a rotating light barrier proposed in patent DE 34 23 538 cannot measure the distance to obstacles; it is limited to the fixed cone shell. Likewise, monitoring requirements that deviate from the cone shell cannot be programmed.

Il &Idigr; C &igr; > O 111

Description:

The invention relates to an optoelectronic protective device for use as machine protection against dangerous machine parts, as reversing monitoring for trucks or as a warning and control device for driverless vehicles. Use as a position detection system is also conceivable.

An optoelectronic distance sensor (3) is located on a rotatably mounted axis (14), driven by a stepper motor (13) or by a motor together with an angle decoder. This determines the distances (10) and the observation angle (11) of any objects (1) that may be present in the radial direction. For this purpose, light pulses are emitted via an LF.D or a laser diode (5), which are focused by a lens system (4) into bundled light beams with a defined beam divergence and are radiated onto existing objects (1). The resulting light spot size (2) on the object (1) depends on the distance (10) of the object (1) from the sensor (3) and is projected onto a photosensitive semiconductor array (6) by a second lens system (4) and converted into a distance-dependent voltage by downstream electronics.

To scan a given area, the distance sensor (3) is swiveled back and forth within the angle range (8). The beam direction can be inclined by an angle (12) relative to the perpendicular to the axis of rotation (14). The movement of the sensor occurs step by step in individual steps, which result from the angular resolution of the distance sensor. In

.-!7J-

When used as a safety system, it is necessary to have the system perform a permanent self-test. For this purpose, a fixed reference object is installed in the field of view, whereby the downstream electronics in a fixed angular position pointing to the reference object determine the expected

In a number of digital memory cells that correspond to the number of steps, distance information is stored for each step, which together form the safety line (7). The object distances measured by the sensor system are compared with the stored distance information for each angle. If the distance information of the object is smaller or larger than the stored information, the corresponding signals are emitted.

By precisely defining the safety area (9) which is defined by \

the safety line (7) is enclosed, it is possible to

To deploy security systems in places that have not yet been

could be monitored. In addition to the possibility of swiveling the entire ■ distance sensor over the scanning area, there is the

Possibility of arranging a rotating mirror in front of the sensor lenses, whereby the transmitted and received light beams are deflected synchronously. Optoelectronic systems are often rendered inaccurate by temperature and long-term drift. In order to guarantee an exact measurement over a longer period of time, a fixed object is placed in the field of view of the optoelectronic distance sensor, whereby the measuring distance to this reference object is used as a reference for the measurements in the remaining angular range, or the measured values obtained are corrected accordingly.

• t ·■··

It ·

Reference distance expected. If the sensor is defective, no measurement or an incorrect measurement would result in the system being switched off and an alarm being triggered.

When using the optoelectronic protection zone device on moving vehicles, it is often necessary to enlarge or reduce the protection zone depending on the speed of the vehicle. Here it is possible to move the programmed safety lines (7) proportionally to the control signal via a control input.

2 Drawings FIG 1, FIG 2 9 Petewfe claims

• » lift It Il Il I* ·!■·

• · aitttiti &igr;

Claims (9)

·· ■· ti · ·■·■·■ i&mdash; · ti · · claims; 1) Optoelectronic protection zone device for securing moving or fixed objects against improper contact or collision, by means of an optoelectronic distance sensor (3) which is pivoted in an adjustable angular range (8), objects (1) are detected with their distance (10) and their angular position (11), characterized in that the distance measurement is carried out by a directed optoelectronic distance sensor which moves with fixed angular steps within a fixed rotation angle (8) in relation to the axis (A) perpendicular to the direction of view and emits a measured value dependent on the distance of the object for each angular step. 2) Optoelectronic protection zone device according to claim 1, characterized in that the distance measurement is effected by optoelectronic distance sensors (3) which emit light pulses via an LED (5) or a LASER diode (5), which are focused by a lens system (4) into bundled light beams with defined beam divergence and beamed onto existing objects (1). The caused light spot size (2) of diffusely reflected light on the object (1) depends on the distance of the object (1) from the sensor (3) and is imaged on a photosensitive semiconductor array (6) by the lens system (4) and converted into a distance-dependent voltage. 3) Optoelectronic protection zone device according to claim 1 or 2, characterized in that programmable safety lines (7) are stored as individual measured values per angular step in electronic memory cells and these are compared with the object positions (10, 11); if the distances determined by the programmable safety lines (7) are undershot, a signal is emitted. 4) Optoelectronic protection zone device according to one of the preceding claims, characterized in that the deflection of the transmitted and detected light beams over the monitoring area is carried out by a mirror which can be rotated in defined angular positions. 5) Optoelectronic protection zone device according to one of the preceding claims, characterized in that the rotational movement of the measuring light beam is caused by a stepper motor. 6) Optoelectronic protection zone device according to one of the preceding claims, characterized in that the rotational movement of the measuring light beam is caused by a driven axis with an attached angle decoder. 7) Optoelectronic protection zone device according to one of the preceding claims, characterized in that the optoelectronic aftjuid sensor measures the distance t «<<&igr; t &bull;'&eegr;'<&igr; ■ &igr;-* O &igr;" &igr; · · of a fixed object in the field of view as a reference distance unit to correct its possible measurement inaccuracy due to drift . 8) Optoelectronic protection zone device according to one of the preceding claims, characterized in that the optoelectronic distance sensor uses the detection of a solid object in the field of view as a self-test to monitor its functionality. 9) Optoelectronic protection zone device according to one of the preceding claims, characterized in that the set safety lines (7) can be shifted by a control signal.