WO1993003399A1

WO1993003399A1 - Obstacle detecting assembly

Info

Publication number: WO1993003399A1
Application number: PCT/SE1992/000544
Authority: WO
Inventors: Carl Gustav ÖHMAN
Original assignee: Aktiebolaget Electrolux
Priority date: 1991-08-07
Filing date: 1992-08-07
Publication date: 1993-02-18

Abstract

An obstacle detecting assembly includes a narrow-beam LED, a wide-beam LED and a light detector. The narrow-beam LED provides range, while the wide-beam LED provides wide coverage at closer range. The assemblies are located about the front of a vacuum cleaner robot and provide warning of obstacles in the robot's path. When an obstacle is first detected, the robot reduces speed and continues until contact or a fixed distance is traveled. The assemblies not only detect obstacles, but also overhanging furniture and steps.

Description

OBSTACLE DETECTING ASSEMBLY

BACKGROUND OF THE INVENTION

The present invention relates to optical proximity sensors and in particular to a control system for a robot. As electronics becomes smaller, lighter, less expensive and more powerful; software becomes more sophisticated; and consumers come to expect more features and more value, the market for autonomous appliances such as robot vacuum cleaners, floor scrubbers and polishers increases. In these applications it is important to come as close as possible to an obstacle in order to clean any and all open areas. In order to keep the cost and complexity of the robot down sensors need to be kept as simple and inexpensive as possible.

SUMMARY OF THE INVENTION

The present invention provides a simple and low cost obstacle detector that provides excellent obstacle detection. The detector is integrated into a control system that provides foi the avoidance of various obstacles to autonomous operation of a cleaning robot. The obstacle detecting assembly includes a first light source having a narrow beam, a second light source having a wide beam, a light detecting means that provides a signal in response to detected light, and a control means that intermittently activates the light sources, receives the signal when a distant obstacle within the narrow beam reflects light from the first source to the light detecting means and receives the signal when a proximate obstacle within the wide beam reflects light from the second light source to the light detecting means. The assembly may also advantageously include a first light blocking means located between the first light source and the light sensing means. The first light blocking means blocks the light detecting means from the first light source. Also included may be a second light blocking means located between the second light source and the light sensing means. The second light blocking means blocks the light detecting means from the second light source. The robot control system includes a plurality of forward obstacle detection sensors facing in a forward direction. These forward obstacle detection sensors provide an early warning signal indicative of the remote presence of an obstacle. Also included is a forward contact sensor. This sensor provides a contact signal indicative of the robot contacting an obstacle. Also included is a control means adapted to receive the signals from the sensors and a drive means adapted to propel the robot in response to the control means. The robot decelerates to a low speed upon receipt of the early warning signal and continues at the slow speed until the first occurring of receipt of the contact signal or a known distance is traveled. The robot control system may also advantageously include a left obstacle detection sensor facing in a direction of between 25 and 50 degrees left of the forward direction and between 25 and 35 degrees up from the forward direction. The left sensor provides a left overhang signal indicative of an overhanging obstacle. Also included may be a right obstacle detection sensor facing in a direction of between 25 and 50 degrees right of the forward direction and between 25 and 35 degrees up from the forward direction. The right sensor provides a right overhang signal indicative of an overhanging obstacle. The robot decelerates to the low speed upon receipt of either overhang signal and continues at the slow speed until the first occurring of receipt of the contact signal or the known distance is traveled. The obstacle detection sensors may advantageously comprise the obstacle detecting assemblies described above. The system may also advantageously include a drop-off sensor facing in a downward direction. The drop-off sensor provides a drop-off (e.g. , a stair step downward) signal indicative of the presence of a drop-off, wherein the robot stops and reverses direction upon receipt of the drop-off signal .

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of an assembly according to the invention.

FIG. 2 is a front elevation view of an assembly according to the invention.

FIG. 3 is a schematic circuit diagram of an assembly according to the invention.

FIG. 4 is a top plan view diagram showing the orientation of the obstacle detection assemblies according to the invention in the forward portion of a vacuum cleaner robot.

FIG. 5 is a block diagram of a robot control system according to the invention.

FIG. 6 is a flow chart diagram of a robot control system according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, an obstacle detecting assembly 10 is shown. A narrow-beam LED 12 having a beam angle A is mounted to a printed-circuit board 14 such that, when energized, the axis of the beam of the LED 12 is projected in a forward and horizontal direction. Similarly, a wide-beam LED 16 having a beam angle B is mounted to the board 14 such that, when energized, the axis of the beam of the LED 16 is projected in a forward and horizontal direction. For example, the angle A may be 16 degrees and the angle B may be 80 degrees. The LED 12 may be, for example, a Siemens SFH-484 and the LED 16 a Siemens SFH-485P. A light detector 18 is mounted on the board 14 between the LED 12 and the LED 16. The detector 18 has an acceptance angle C about the same as the angle B and an beam axis parallel to those of the LED 12 and the LED 16. In the preferred embodiment the light detector 18 is an integrated package that includes a modulation pulse circuit to control an LED and a demodulation circuit to detect light in synchronism with the pulse circuit while rejecting ambient light. The light detector 18 may be, for example, a Sharp IS441F. A light-blocking wall 20 is mounted on the board 14 between the LED 12 and the light detector 18 to prevent light from the LED 12 from impinging directly on the light detector 18. Similarly, a light-blocking wall 22 is mounted on the board 14 between the LED 16 and the light detector 18. Referring to FIG. 3, a schematic diagram of the obstacle detecting assembly 10 is shown. The power terminal 24 of the light detector 18 is connected to a power source +V (e.g-. , +5 volts). A capacitor 26 (e.g. , 100 microfarads, 10 volts) is connected between +V and ground. One terminal of a resistor 28 (e.g., 2 ohms) is also connected to +V. The other terminal of the resistor 28 is connected to the anode of the LED 12. The cathode of the LED 12 is connected to the anode of the LED 16. The cathode of the LED 16 is connected to the emitter of a pnp transistor 30. The collector of the transistor 30 is connected to ground. The base of the transistor 30 is connected to one terminal of a resistor 32 (e.g. , 1,000 ohms) . The other terminal of the resistor 32 is connected to the modulator output terminal 34 of the light detector 18. The common terminal 36 of the light detector is connected to ground. The output of the light detector 18 appears on the detector output terminal 38. In operation, the light detector 18 provides a periodic pulse train (e.g. , a few microseconds out of each fraction of a millisecond) from the modulator output terminal 34 to the base of the transistor 30. This briefly turns on the transistor 30, allowing current to flow th. jgh the LEDs 12, 16. The capacitor 26 stores energy from +V during the time the transistor 30 is off, then provides a large current (0.3 amperes ) through the LEDs 12, 16 when the transistor 30 is pulsed. The resistor 28 limits current through the LEDs 12, 16. Because of the low duty cycle of the periodic pulse train from the modulator output terminal 34, the average current through the LEDs 12, 16 is low (e.g., 15 milliamperes) . When current flows through the LEDs 12, 16, they emit light (e.g., at 880 nanometers). The LED 12 emits a narrow beam of light with a relatively large power density. On the other hand, the LED 16 emits a wide beam of light with a relatively small power density. When light from the LEDs 12, 16 strikes an obstacle, a portion of the light is reflected b.;:_k to the light detector 18. When this reflected light is detected by the light detector 18, the light detector 18 provides a voltage on the terminal 38 indicative thereof. Because of its larger power density, the beam from the LED 12 has a greater range than that of the LED 16, but it provides a limited field of view. Conversely, the LED 1 has a shorter range, but a much wider field of view. By combining the LEDs 12, 16, both good range and wide coverage are provided. The LED 12 provides light for detecting distant obstacles and the LED 16 provides light for detecting proximate obstacles in a wide field of view. Referring to FIG. 4, the forward portion of a vacuum cleaner robot 100 is shown. A group of four forward obstacle detection sensors 101, 102, 103, 104 are arranged at the front of the robot 100. Each of the sensors 101, 102, 103, 104 has a forward-looking detection axis D, E, F, G, respectively. This arrangement provides effective coverage of the area in front of the robot 100. A left overhang obstacle detection sensor 105 is located at the left front corner of the robot 100. The sensor 105 has a detection axis H of between 25 and 50 degrees (e.g., 40 degrees) left from the forward direction. In addition, the axis H is oriented from 25 to 35 degrees upward (e.g. , 30 degrees) . The sensor 105 detects obstacles that the robot 100 may be turning towards. In addition, the sensor 105 detects when the robot 100 starts under an overhanging obstacle such as a table or bed. A right overhang obstacle detection sensor 106 is located at the right front corner of the robot 100. The sensor 106 has a detection axis I of between 25 and 50 degrees (e.g. , 40 degrees) right from the forward direction. In addition, the axis I is oriented from 25 to 35 degrees upward (e.g. , 30 degrees). The sensor 106 detects obstacles that the robot 100 may be turning towards. In addition, the sensor 106 detects when the robot 100 starts under an overhanging obstacle such as a table or bed. Each of the sensors 101, '102, 103, 104, 105, 1CT6 comprises an obstacle detecting assembly 10, except that the sensors 105, 106 have reduced sensitivity to allow the robot 100 to run close to objects at its side, such as walls. The sensors 101, 102, 105 are connected to a left early warning signal terminal 108 and the sensors 103, 104, 106 are connected to a right early warning signal terminal 110. The terminals 108, 110 receive the signal from respective detection assembly 10 output terminals 38. By differentiating between right and left located obstacles the robot 100 may be programmed to steer around obstacles. A left drop-off sensor 116 is also located in the left front of the robot 100 and a right drop-off sensor 118 is also located in the right front of the robot 100. The sensors 116, 118 each have an unshown downward pointing LED and light detector 18. If the robot 100 encounters a downward step or other drop-off, no light is reflected to the light detector 18 and the affected sensors 116, 118 provide a signal to a left drop-off signal terminal 120 and a right drop-off signal terminal 122, respectively. Here, the function is reversed: no light reflected means stop the robot. A left contact sensor 124 is provided on the left forward and "orner edges of the robot 100. When the contact sensor 124 contacts an obstacle, a signal is provided to a contact signal terminal 126. A right contact sensor 125 is provided on the right forward and corner edges of the robot 100. When the contact sensor 125 contacts an obstacle, a signal is provided to a contact signal terminal 127. Referring to FIG. 5, a control system for the robot 100 is shown. A CPU 130 controls drive motors 132 under control of a program contained in a memory 134 and in response to the forward sensors 101, 102, 103, 104, the contact sensor 124, the overhang sensors 105, 106 and the drop-off sensors 116, 118. The CPU 130 responds to signals on the terminals 108, 110, 120, 122, 126, 127. Referring to FIG. 6, a flow chart diagram of the contrόQ. system for the robot 100 is provided. The robot 100 is . travelling forward at normal speed (e.g. , 1 foot/second) at the start of the diagram of FIG. 6. The CPU 130 checks the contact sensors 124, 125 and the drop-off sensors 116, 118 for signals indicating physical contact of the robot 100 with an obstacle or an imminent drop-off, respectively. If such a signal is received, the CPU 130 stops the drive motors 132 (and additionally would back up the robot 100 and steer to avoid the problem) . If no contact or drop-off is sensed, the CPU 130 checks the sensors 101, 102, 103, 104, 105, 106 for early warning of a remote obstacle (or overhang) . If no early warning is received the CPU starts through the check of all the sensors 124, 125, 116, 118, 101, 102, 103, 104, 105, 106 again. If an early warning is received the CPU 130 slows the drive motors 132 to slow speed (e.g., 10 to 15 percent of normal speed) . The robot 100 then continues at this slow speed until: contact with an obstacle produces a contact signal from either the left contact sensor 124 or the right contact sensor 125; a drop-off is detected by the drop-off sensors 116, 118; or the robot 100 has travelled a distance X (e.g., 1 foot). Upon the first happening of contact, drop- off or the distance X travelled, the CPU 130 stops the drive motors 132 (and additionally would back up the robot 100 and steer to avoid the problem) . The operation of the robot 100 at slow speed in the vicinity of obstacles minimize the chance of the robot 100 damaging itself or the obstacle when contact is finally made. This not only allows rapid operation for most of the time, but also allows the robot 100 to clean as close to obstacles as possible (i.e. touching) without damage. It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.

Claims

WHAT IS CLAIMED IS:

1. An obstacle detecting assembly comprising:

a first light source having a narrow beam;

a second light source having a wide beam;

a light detecting means, said light detecting means providing a signal in response to detected light; and

a control means, said control means intermittently activating said light sources, receiving said signal when a distant obstacle within said narrow beam reflects light from said first source to said light detecting means and receiving said signal when a proximate obstacle within said wide beam reflects light from said second light source to said light detecting means.

2. An assembly according to claim 1, further comprising:

a first light blocking means located between said first light source and said light sensing means, said first light blocking means blocking said light detecting means from said first light source; and

a second light blocking means located between said second light source and said light sensing means, said second light blocking means blocking said light detecting means from said second light source.

3. An obstacle detecting assembly comprising:

a mounting member; a first light source having a narrow beam, said first light source being attached to said mounting member and being oriented with said narrow beam in a known direction;

a second light source having a wide beam, said second light source being attached to said mounting member and being oriented with said wide beam in said known direction;

a light detecting means having a wide acceptance angle, said light detecting means being attached to said mounting member and being oriented with said wide acceptance angle in said known direction and providing a signal in response to detected light;

a first light blocking means, said first blocking means being attached to said mounting member and oriented to block said first light source from said light detecting means;

a second light blocking means, said second blocking means being attached to said mounting member and oriented to block said second light source from said light detecting means ; and

a control means, said control means intermittently activating said light sources, receiving said signal when a distant obstacle within said narrow beam reflects light from said first source to said light detecting means and receiving said signal when a proximate obstacle within said wide beam reflects " light from said second light source to said light detecting means.

4. A robot control system for enabling a robot to avoid obstacles comprising:

a plurality of forward obstacle detection sensors facing in a forward direction, said forward obstacle detection sensors providing an early warning signal indicative of the remote presence of an obstacle;

a forward contact sensor, said contact sensor providing a contact signal indicative of said robot contacting an obstacle ;

a control means adapted to receive said signals from said sensors; and

a drive means adapted to propel said robot in response to said control means, wherein said robot decelerates to a low speed upon receipt of said early warning signal and continues at said slow speed until the first occurring of receipt of said contact signal or a known distance is traveled.

5. A robot control system according to claim 4 , further comprising:

a left obstacle detection sensor f 'jing in a direction of between 25 and 50 degrees left of said forward direction and between 25 and 35 degrees up from said forward direction, said left sensor providing a left overhang signal indicative of an overhanging obstacle; and

a right obstacle detection sensor, facing in a direction of between 25 and 50 degrees right of said forward direction and between 25 and 35 degrees up from said forward direction, said right sensor providing a right overhang signal indicative of an overhanging obstacle, wherein said robot decelerates to the low speed upon receipt of either overhang signal and continues at said slow speed until the first occurring of receipt of said contact signal or the known distance is traveled.

6. A robot control system according to claim 4 , wherein said obstacle detection sensors comprise:

a first light source having a narrow beam;

a second light source having a wide beam; and

a light detecting means, said light detecting means providing said early warning signal in response to detected light, wherein said control means intermittently activates said light sources, receives said early warning signal when a distant obstacle within said narrow beam reflects light from said first source to said light detecting means and receives said signal when a proximate remote obstacle within said wide beam reflects light from said second light source to said light detecting means.

7. A robot control system according to claim 4, further comprising a drop-off sensor facing in a downward direction, said drop-off sensor providing a drop-off signal indicative of the presence of a drop-off, wherein said robot stops and reverses direction upon rece^'ipt of said drop-off signal.