EP3086910A1

EP3086910A1 - Impact detection system for robotic device

Info

Publication number: EP3086910A1
Application number: EP14823998.1A
Authority: EP
Inventors: Adolfo Suarez Roos
Original assignee: Airbus Group SAS
Current assignee: Airbus SAS
Priority date: 2013-12-26
Filing date: 2014-12-23
Publication date: 2016-11-02
Also published as: CN106029309A; FR3016039A1; CN106029309B; US20160318188A1; FR3016039B1; WO2015097215A1

Abstract

The invention relates to an impact detection system for a robotic device. According to the invention, said system comprises: a flexible covering element (10) for enveloping part of said robotic device, said covering element (10) defining an inner air volume; at least one sensor (12) for measuring the differential pressure between the pressure in said inner air volume and the pressure outside said covering element (10); and a detection unit (13) designed to receive the measuring signal of said at least one sensor (12), to carry out an analysis, on the basis of said measuring signal, in order to detect a sudden variation in said pressure, and to emit a stop signal to said robotic device when such a variation is detected.

Description

Impact detection system for robotic device

BACKGROUND OF THE INVENTION

Field of the invention

The present invention relates to an impact detection system for a robotic device.

The invention also relates to a robotic device equipped with at least one such detection system.

Technological background

It is known that when a robot shares a work space with one or more operators, the protection of this or these operators as well as the robot becomes an absolute priority.

This robot can, in fact, by making a movement, for example a rotation of an arm, to strike an operator in the field of movement of this arm. The operator who is thus touched can be injured if the shock is sufficiently violent.

To guarantee the safety of operators, physical barriers such as grilles, or light curtains such as optical systems are commonly implemented.

However, these barriers induce a modification of the workspace with the creation of restricted access areas, the positioning of many visual signs such as footprints or the addition of additional organs to ensure the transfer of objects between the area reserved for the robot and the area reserved for the operators. In addition, noisy audible alarms can also be used to warn the operator of the robot's start-up or incursion into the robot's zone.

All these barriers are tedious to install and expensive. In addition, they restrict the workspace of the operators.

Sensitive skins based on matrix distributions of sensory sensors capable of detecting a contact are also known.

However, the manufacture of these detectors is relatively complex and expensive and is only used on small surfaces.

There are still known tactile surfaces comprising two conductive or resistive materials for detecting a contact by electrical resistivity measurements.

However, the manufacture of these detectors can be complex and above all, the measurements may not be uniform and therefore reliable.

The present invention aims at overcoming these various disadvantages of the prior art by proposing an impact detection system for a robot that is simple in its design and in its operating mode, which is economical and has a very high sensitivity for measuring impacts of the same type. very low energies.

Another object of the present invention is such a system allowing the detection of the point of impact reliably and quickly.

BRIEF DESCRIPTION OF THE INVENTION

For this purpose, the invention relates to an impact detection system for a robotic device.

According to the invention, this detection system comprises:

a flexible covering element for enveloping or covering a portion of said robotic device, said covering element delimiting an interior air volume,

at least one sensor for measuring the differential pressure between the pressure in said interior air volume and the external pressure of said covering element,

a detection unit configured to receive the measurement signal of said at least one sensor, to perform on the basis of said measurement signal an analysis for detecting an abrupt variation of said pressure and to emit a stop signal to said robotic device when such a variation is detected. "Sudden variation" of pressure is understood to mean a high frequency variation of this pressure such as that resulting from the generation of a sound wave propagating in said interior volume following an impact on said covering element.

The pressure outside said cover member is typically the pressure in the area such as a room or hall, in which the robotic device is placed. This external pressure will therefore generally be atmospheric pressure but not necessarily.

Said part of said robotic device being mobile, the thickness of said cover element is preferably less than 15 mm and more preferably 10 mm so as not to limit the movements of said moving part.

Such an impact detection system advantageously makes it possible to very significantly improve the safety of the robots and thus allow their use near the operators with greater security.

Indeed, this detection system allows:

- detect any collision and stop the robot before irreversible injuries can occur, and

- to reduce the effects of an impact by distributing the contact force over a wide surface and / or by the use of flexible materials.

Advantageously, such a detection system comprising one or more sensors not distributed over the entire skin, such as devices of the state of the art but located on the edges of this skin, fewer sensors are necessary and the wiring of these sensors is easier.

In different particular embodiments of this detection system, each having its particular advantages and susceptible to many possible technical combinations:

this system comprises at least two sensors for measuring the differential pressure.

The implementation of at least two sensors provides the necessary redundancy in case of failure / malfunction of one of the sensors.

The implementation of three or more sensors, that is to say at least three sensors, to determine the position of impact by triangulation.

Having found the impact position with good precision, it becomes possible to adapt the reaction of the robot in the best way and even to take advantage of this information to facilitate the control of the robot. said cover member comprises a flexible material permeable to air, said material being covered with a sealed wall on at least one of its faces.

Preferably, said covering element comprises two flexible walls assembled on their periphery in a sealed manner delimiting between these two walls an internal volume in which is placed the flexible material. For purely illustrative purposes, the flexible waterproof wall is made of flexible plastic material or rubber.

Advantageously, said flexible air permeable material is selected from the group consisting of foam, open cell foam, fibrous wadding, elastic component and combinations thereof.

said covering element is a self-inflating mat, said detection unit comprises, for each sensor, an electronic circuit comprising an impedance matching stage at the output of which are placed two resistors for separating the signal coming out of this stage of impedance matching in two signals, each signal being sent to a separate input of a comparator, a detector for measuring a signal output of said comparator corresponding to a pressure variation for a time Δΐ.

The electronic system can alternatively be completely analog: the sensor signal is digitally filtered to obtain the same result.

this system comprises a security interface intended to be placed between said cover element and said part of the robotic device, said security interface being able to detect a pressure applied on said interface and to send an alarm signal to a control unit said control unit sending a stop signal to said robotic device when it receives such an alarm signal.

As a purely illustrative example, this interface may be made with a sensitive skin comprising in its thickness two spaced apart conductive materials, which transmit a signal when they come into contact under the effect of a shock.

said at least one sensor is intended to be mounted directly on said robotic device or is deported with respect to said element of covering not to form a hard point on said cover member,

this system comprises a probe for measuring the pressure in said interior volume,

this system comprises an inflation device for maintaining a constant pressure in said interior volume.

Advantageously, this pressure Pfonctionnement is of the order of 3 to 4 bars to ensure good sensitivity of the detection system impacts.

The present invention also relates to a robotic assembly comprising a robotic device and a detection system as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages, aims and particular features of the present invention will emerge from the description which follows, for an explanatory and non-limiting purpose, with reference to the appended drawings, in which:

FIG. 1 schematically represents an impact detection system for a robot according to a particular embodiment of the present invention,

FIG. 2 is a schematic view of the detection unit of the system of FIG. 1,

FIG. 3 shows a skin equipped with two sensors of the system of FIG. 1,

FIG. 4 shows a robot of which a part of the articulated arm is covered with a skin as shown diagrammatically in FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENTS OF

THE INVENTION

First, we note that the figures are not scaled.

Figures 1 to 3 describe an impact sensing system for a robot according to a particular embodiment of the present invention. This robot is here placed in a building at atmospheric pressure Pr _a tm

This system comprises a flexible cover element, or sensitive skin, for covering a part of this robot such as its arm (not shown), which is likely to collide with an object or a person during its movement. This covering element 10 is here a self-inflating mat comprising a foam bagged in a sealed plastic envelope. This self-inflating mattress 10 defines a volume 1 1 of indoor air with an internal pressure Pr _int .

The covering element 10 being flexible and inflated, it advantageously defines a protective barrier capable of absorbing light impacts.

In addition, this covering member 10 automatically maintaining its shape, it does not require any inflation device and is therefore always operational.

As shown in Figure 1, the system also includes two sensors 12 offset at the ends of the cover member 10 so as not to form a hard point on the outer surface of this element.

These sensors 12 measure the differential pressure between the pressure Pr _int in the volume 1 1 of indoor air defined by the covering element 10 and the atmospheric pressure P r _a t _m

It is thus possible to have access to variations in the pressure of the air enclosed by the covering element.

However, during an impact on the covering element 10, a pressure wave 13 traverses the interior of the volume delimited by the self-inflating mattress 10 generating a pressure disturbance which is detected by the two sensors 12.

These measurements are then sent to a detection unit 13 configured to receive the measurement signals of the two sensors 12, to execute for each signal an analysis to detect a sudden variation of said pressure and to emit a stop signal to the robot when a such variation is detected.

As represented in FIG. 2, for each sensor 12, the detection unit 13 comprises an electronic circuit associated only with this sensor and comprising a first operational amplifier 14 at the output of which two resistors 15, 16, each going on a separate input of a second operational amplifier 17, the values of the resistors 15, 1 6 being identical or as close as possible.

The inverting input 171 of the second operational amplifier 17 is connected to ground by a capacitor 18, the assembly formed by the resistor 16 and the capacitor 18 forming a low-pass filter on the inverting input 171 of the second operational amplifier 17.

On the inverting input side 171 of the operational amplifier 17, the capacitor 18 / resistor 1 6 assembly removes all the high frequencies of the signal and passes only the low frequencies.

Positive input side 172 of the operational amplifier 17, everything passes, including the pressure variations from the impacts on the element 10 covering.

The second operational amplifier 17 mounted as a comparator gives its output a signal equal to 1 (high level) during a variation of pressure throughout the duration Δΐ of this variation. A microcontroller (not shown) then makes it possible to measure the signal at the output of the second operational amplifier.

The resistor 19 placed at the output of the second operational amplifier

17 adds a hysteresis to the output, preventing the occurrence of oscillations when the two input levels of the second operational amplifier are very close.

Furthermore, a smoothing is performed by the capacitor placed between the inverting terminal of the second operational amplifier 17 and the ground. This circuit also has a pull-up resistor 20 so that the comparator does not trigger on the noise present on the non-inverting input.

This circuit advantageously allows the detection of minute pressure variations and has a very high reactivity and a very short rise time. For purely illustrative purposes, this rise time is here of the order of 100 nanoseconds.

The signals sent to the comparator 17 are not identical because a branch of the electronic circuit has a capacity inducing a delay, and can therefore vary only slowly. In addition, a pull resistance causes the voltage to rise slightly, so that the sensor noise does not generate bad detections. The second branch of the electronic circuit varies quickly.

Advantageously, this detection system allows the determination of the point of impact on the surface of the covering element.

In addition, it is found that the detection system works even when it shows slight leaks. It is also observed that the variations in the external pressure of said covering element such as atmospheric pressure, and, for example, linked to meteorological conditions or still resulting from rapidly closing doors, are sufficiently slow and uniform for the detection system to react. not.

The use of several sensors 1 2 provides redundant detection making the detection system more secure. It also offers the possibility of triangulating the signals sent by the sensors 1 2 in order to estimate the contact position on the surface of the covering element.

In a particular embodiment where this system comprises three sensors for measuring the differential pressure Ci, C ₂ and C ₃ and in the case where the sensor Ci is the first to detect a pressure disturbance, the sensor C ₂ being the second and the sensor C ₃ being the third to detect this disturbance. Then the measurement time differences are respectively (t ₂ -ti) and (t ₃ -ti).

Considering that the distance separating the point of impact from the position of the sensor Ci is r, it follows that the distances separating the point of impact of the sensors C ₂ and C ₃ are respectively r + cx (t ₂ -ti) and r + cx (t ₃ -ti) where c is the speed of propagation of the wave in the interior volume of the cover member.

For curved elements, we consider that the wave propagates on a median virtual surface.

The intersection of the curves obtained by considering a step Ar around the distance r makes it possible to obtain the position of the point of impact in a very short time and with a very high precision by an iterative algorithm.

Claims

1. Impact detection system for a robotic device, characterized in that it comprises:

a flexible covering element (10) for wrapping a part of said robotic device, said covering element (10) delimiting an interior air volume,

at least one sensor (12) for measuring the differential pressure between the pressure in said interior air volume and the external pressure of said covering element (10),

a detecting unit (13) configured to receive the measurement signal of said at least one sensor (12), performing on the basis of said measurement signal an analysis for detecting an abrupt variation of said pressure and emitting a stop signal to said sensor robotic device when such variation is detected, and in that

said covering element (10) comprises a flexible material that is permeable to air, said material being covered with a sealed wall on at least one of its faces, said covering element (10) forming a self-inflating mat.

2. Detection system according to claim 1 characterized in that it comprises at least two sensors (12) for measuring the differential pressure.

3. Detection system according to claim 1 or 2, characterized in that said flexible material permeable to air is selected from the group comprising a foam, an open cell foam, a fibrous wadding, at least one elastic component and combinations of these elements.

4. Detection system according to any one of claims 1 to 3, characterized in that said detection unit (13) comprises, for each sensor (12), an electronic circuit comprising a stage (14) of adaptation of output impedance of which two resistors (15, 1 6) are arranged to separate the output signal from said one impedance matching stage (14) into two signals, each signal being sent to a separate input of a comparator (17) , a detector for measuring a signal at the output of said comparator corresponding to a variation of pressure during a time Δΐ.

5. Detection system according to any one of claims 1 to

4, characterized in that it comprises a security interface intended to be placed between said covering element (10) and said part of the robotic device, said security interface being able to detect a pressure applied on said interface and to send a alarm signal to a control unit, said control unit sending a stop signal to said robotic device when it receives such an alarm signal.

6. Detection system according to any one of claims 1 to

5, characterized in that said at least one sensor (12) is intended to be mounted directly on said robotic device or is offset with respect to said covering element (10) so as not to form a hard point on said element (10) of recovery.

7. Detection system according to any one of claims 1 to

6, characterized in that it comprises a probe for measuring the pressure in said interior volume.

8. Detection system according to any one of claims 1

7, characterized in that it comprises an inflation device for maintaining a constant operating pressure P in said interior volume.

9. Robotic assembly comprising a robotic device and a detection system according to any one of claims 1 to 8.