WO2009052616A1

WO2009052616A1 - Two wire digital ultrasonic sensor using bi-directional power line communication

Info

Publication number: WO2009052616A1
Application number: PCT/CA2008/001862
Authority: WO
Inventors: Matthew T. Burtch; Guner R. Sarioglu; Ryan Xue
Original assignee: Magna International Inc.
Priority date: 2007-10-23
Filing date: 2008-10-23
Publication date: 2009-04-30
Also published as: EP2215499A4; BRPI0818879A2; CN101868736A; EP2215499A1

Abstract

A circuit arrangement having a master microcontroller operably connected to a sensor for detecting a parameter. The sensor and microcontroller are connected to a power source where a microcontroller power line is connected between the power source and the master microcontroller. A power communications line is connected between the power source, master microcontroller, and sensor, wherein the power communications line carries power to the sensor as well as communication signals between the sensor and the master microcontroller.

Description

TWO WIRE DIGITAL ULTRASONIC SENSOR USING BI-DIRECTIONAL POWER LINE COMMUNICATION

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a PCT International Application of United States

Patent Application No. 61/000,091 filed on October 23, 2007. The disclosure of the above application is incorporated herein by reference. This application claims the benefit of U.S. Provisional Application No. 60/000,091 , filed October 23, 2007.

FIELD OF THE INVENTION

The present invention relates to sensor control circuits having two input wires.

BACKGROUND OF THE INVENTION

Sensor circuits have been utilized in automotive applications for providing a measure of data for a given parameter that is being monitored. For example, sensors are used in engine components for the purpose of determining the position of various valves or actuators during normal operation. Additionally, sensors have also been incorporated to measure environmental factors such as temperature, light, and objects external to the vehicle. Most sensor circuitry utilizes three wires for communicating between the sensor, microcontroller, and power source. For example, two wires will be used for supplying power to the microcontroller and sensor unit. A third wire is used for communicating with the sensor unit. Reducing the number of wires and connections is desirable from the stand point of saving manufacturing time, equipment, as well as reducing the possibility of equipment failure by virtue of the fact that a lesser number of wires are being used. Thus, it is desirable to develop sensor circuits that need fewer than 3 wires between the microcontroller and the sensor. SUMMARY OF THE INVENTION

The present invention is directed to a circuit arrangement having a master microcontroller operably connected to a sensor for detecting a parameter. The sensor and microcontroller are connected to a power source where a microcontroller power line is connected between the power source and the master microcontroller. A power communications line is connected between the power source, master microcontroller, and sensor, wherein the power communications line carries power to the sensor as well as communication signals between the sensor and the master microcontroller.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: Fig. 1 is a schematic of the two wire sensor circuitry; Fig. 2a is a graph showing voltage versus time when the logic signal value is 1 ;

Fig. 2b is a graph showing voltage versus time when the logic signal value is 0;

Fig. 3 depicts graphical examples of a communications scheme for the circuit arrangement;

Fig. 4 is a perspective view of the sensor circuit as incorporated in a two wire ultrasonic sensor arrangement; and Fig. 5 depicts a perspective view of the vehicle having a plurality of ultrasonic sensors connected to the vehicle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Fig. 1 is a schematic view of a circuit arrangement 10 having a master microcontroller 12, a power source 14, and a sensor 16. The circuit arrangement 10 in one embodiment of the invention is a two wire digital or active environmental sensor used to sense objects in the external vehicle environment. The sensor 16 can be, but is not limited to a traffic environment sensor, weather sensor and an object sensor. However, the scope of this invention is not limited to environmental sensors or digital technology. The sensor 16 is an ultrasonic type sensor that utilizes sonar or sound waves to detect the presence or absence of an object as well as the distance from the object. One particular embodiment of the invention shown in Fig. 5 depicts the sensor as being used as an active ultrasonic park assist sensor. However, it is within the scope of this invention for the sensor 16 to be any type of sensor for detecting a given parameter while being able to operate using the two wire technology. Both the sensor 16 and the microcontroller 12 are connected to the power source 14. The power source 14 in this particular circuit arrangement 10 has a power source level that is a 5 volt direct current power source such as a battery. The use of a 5 volt power source with this circuit arrangement 10 provides a significant advantage over other arrangements that typically use a 12 volt power source. Using a 5 volt power source allows the circuit arrangement to be connectable to the same power source as the vehicle electronic control unit which also uses a 5V power source. However, it is possible to have a different type of power source having a different voltage depending upon the particular needs of an application. For example any types of voltage power source can be used, however, it is contemplated that 6 volts and 12 volt power sources are within the scope of this invention.

The power source 14 is connected to the microcontroller 12 through a microcontroller power line 18. The sensor 16 receives power through a sensor power line 20 which is connected to a power communications line 22 that is connected to both the power source 14 and the microcontroller 12. The power communications line 22 transmits both power as well as bit line encoding that is both received by the sensor and sent to the microcontroller 12.

The sensor power line 20 has a capacitor 24 disposed on the sensor power line 20 and a diode 26 that separates the capacitor 24 and sensor power line 20 from the power communications line 22. The diode 26 allows power flow from the power source 14 to the capacitor 24, but does not allow power to flow in the direction from the capacitor 24 past the diode 26. The capacitor 24 is configured to supply power to sensor 16 during voltage drops. While this particular embodiment of the invention describes a capacitor 24 being used, it is possible for another suitable energy storage device to be used, such as a battery, switch capacitor or an inductor. Connected between the power source 14 and the power communications line 22 is a high impedance line 28, which is an energy line having a high impedance resistor 30. A low impedance line 32 having a low impedance resistor is also connected to the power source 14. The low impedance resistor 34 has a resistivity that is lower than the high impedance resistor 30. The low impedance line 32 and high impedance line 28 run in parallel. However, the low impedance line 32 has an impedance switch 36 that is controlled by the master microcontroller 12. When the impedance switch 36 is open, higher current passes through the power communications line 22 and onto the capacitor 24. When the impedance switch 36 is closed, a lower current will pass through the power communications line 22. It is during this period of lower current in the power communications line 22 that the line can be used for carrying a communications signal between the master microcontroller 12 and the sensor 16.

The master microcontroller 12 has a microcontroller communications line 38 that is connected to the power communications line 22. The microcontroller communications line 38 is also connected to ground. A master microcontroller output 40 is connected to the microcontroller communications line 38 through a master microcontroller output switch 42. When the master microcontroller switch 42 is closed, signals are sent from the microcontroller 12 through the master microcontroller output 40 and onto the power communications line 22. The master microcontroller 12 also has connected to it a master microcontroller input 44 that is also connected to the microcontroller communications line 38 and receives signals from the sensor 16 via the power communications line 22.

The sensor 16 has a sensor communications line 46 that is connected to the power communications line 22 and ground. The sensor 16 has a slave sensor input 48 that selectively receives signals from the microcontroller 12 that are outputted through the master microcontroller output 40. The slave sensor input 48 introduces command signals to the sensor 16 that can cause the sensor to carry out a function such as sending and receiving ultrasonic sound waves. The sensor 16 in carrying out its functions will receive signals that are indicative of its function. For example, an ultrasonic sensor will receive signals that indicate the presence of an object in the path of the sensor 16. The signals received by the sensor 16 are transmitted to the microcontroller 12 through a slave sensor output 50. The slave sensor output 50 is controlled by a slave sensor switch 52 that will allow for signals to be transmitted from the slave sensor output 50 when the slave sensor switch 52 is in the closed position. When the slave sensor output switch 52 is in the open position the sensor communications line 46 will go to ground.

The operation of the circuit arrangement 10 is controlled by signals generated from the master microcontroller 12. During initial start up of the sensor 16 the master microcontroller 12 will cause the impedance switch 36 to be open which allows more power to flow through the power communications line 22 to charge the capacitor 24. During periods that communications signals are transmitted to the sensor 16 the impedance switch 36 is closed in order to impede the power supply and allow the power communications line 22 to carry a communications signal. The communications signals are generated between the master microcontroller 12 and the sensor 16 through the input and output ports connected to the microcontroller communications line 38 and the sensor communications lines 46. However, the sensor 16 can encounter power fluctuation or voltage drops due to communication that can impair or disrupt sensor functions. The present invention solves this problem by using the capacitor 24 to supply voltage during the period of power loss or fluctuation.

Figs. 2a and 2b depict two graphs, which both exemplify the data line bit encoding for the circuit arrangement 10. Fig. 2a depicts the bit encoding when the logic value is set at 1 and Fig. 2b depicts the bit encoding when the logic value is set at 0. The data line bit encoding depicted in Figs. 2a and 2b is distinct from other circuit arrangements for ultrasonic sensors because when the logic value is at 0, there is a pulse of 5 volts for 50 microseconds instead of the voltage being 0. When the logic value is 1 , there is a pulse of 5 volts for 100 microseconds. This permits the capacitor to be receiving a voltage charge even when the logic value is at 0 when compared to other system where the voltage value would be 0 when the logic value is 0. It also allows for communications data to be constantly transmitted through the power communications line 22, even when the logic value is 0.

Fig. 3 depicts an example of a communications scheme signals between the microcontroller 12 and the sensor 16 during various phases of sensor operation.

Fig. 4 is a perspective view of the sensor circuit as incorporated in a two wire ultrasonic sensor arrangement 100. An ultrasonic sensor 102 has a power communications line 104 that extends to a circuit box 106 that contains the circuit arrangement 10 shown in Fig. 1. The power source connector 108 has two wires extending from the connector into the circuit box 106. One of the wires provides power to the master microcontroller and the other wire provides power to the circuit arrangement 10 that leads to the power communications line 104.

Fig. 5 depicts a vehicle 200 having a plurality of ultrasonic or traffic environment sensors 202 connected to a bumper 204 of the vehicle 200. In this embodiment, the plurality of ultrasonic sensors 202 are used as proximity sensors for alerting a driver of the vehicle 200 when objects are in the path of the vehicle 200 as the vehicle is backing up. The traffic environment sensors depicted on the vehicle 200 are used primarily for determining the presence or absence of an object in the path of the vehicle 200 while backing up. It is possible for the traffic environment sensors 202 to be used in other areas of the vehicle for providing proximity detection. For example, such sensors can be used for collision avoidance, parking assist, security, and other suitable uses where the detection of objects on the outside environment of the vehicle are desired.

The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Claims

1. A circuit arrangement for an active traffic environment sensor comprising: a master microcontroller; a sensor configured for active traffic environment sensing; a power source; a microcontroller power line connected to said master microcontroller which receives power from said power source and said master microcontroller; and a power communications line connected between said power source, said master microcontroller, and said sensor, wherein said power communications line carries power for said sensor and communications signals between said master microcontroller and said sensor.

2. The circuit arrangement for an active traffic environment sensor of claim 1 , further comprising: a low impedance line connected to said power source, said low impedance line having a resistor formed thereon; a high impedance line connected to said power source having a resistor formed thereon, wherein said resistor of said high impedance line has a greater resistivity than the resistor of said low impedance line.

3. The circuit arrangement for an active traffic environment sensor of claim 2, wherein the power source is a 5 volt direct current power source.

4. The circuit arrangement for an active traffic environment sensor of claim 2, further comprising an impedance switch formed on said low impedance line, wherein said impedance switch is controlled by said master microcontroller to control the flow of power through said low impedance line.

5. The circuit arrangement for an active traffic environment sensor of claim 1 , further comprising a capacitor operably connected to said power communications line between said sensor and said master microcontroller.

6. The circuit arrangement for an active traffic environment sensor of claim 5, further comprising a diode operably connected to said power communications line between said capacitor and said master microcontroller and said power source.

7. The circuit arrangement for an active traffic environment sensor of claim 1 , further comprising a master microcontroller output connected to said master microcontroller; and a slave sensor input connected to said sensor, wherein said slave sensor input receives signals from said master microcontroller output.

8. The circuit arrangement for an active traffic environment sensor of claim 7, further comprising: a slave sensor output connected to said sensor for outputting signals from said sensor; and a master microcontroller input connected to said master microcontroller for receiving signals from said slave sensor output.

9. A circuit arrangement for an active traffic environment sensor comprising: a master microcontroller; a sensor configured for active traffic environment sensing having a communications port and a sensor power line; a power source; a microcontroller power line connected between said power source and said master microcontroller; a power communications line connected between said power source, said master microcontroller, and said sensor, wherein said sensor power line branches off of said power communications line; a capacitor on said sensor power line; and a diode between said capacitor and said power communications line.

10. The circuit arrangement for an active traffic environment sensor of claim 9, further comprising: a low impedance line connected to said power source, said low impedance line having a resistor formed thereon; a high impedance line connected to said power source having a resistor formed thereon, wherein said resistor of said high impedance line has a greater resistivity than the resistor of said low impedance line and said low impedance line and said high impedance line are positioned in parallel and connect said power source to said power communications line.

11. The circuit arrangement for an active traffic environment sensor of claim 10, wherein said power source is a 5 volt direct current power source.

12. The circuit arrangement for an active traffic environment sensor of claim 10, further comprising an impedance switch formed on said low impedance line, wherein said impedance switch is controller by said master microcontroller and receives commands from said master microcontroller to open and close said impedance switch to control the flow of power through said low impedance line.

13. The circuit arrangement for an active traffic environment sensor of claim 9, further comprising a master microcontroller output connected to said master microcontroller, wherein said master microcontroller output is configured to send signals to said power communications line; and a slave sensor input connected to said sensor for receiving signals from said master microcontroller output through said power communications line.

14. The circuit arrangement for an active traffic environment sensor of claim 13, further comprising a slave sensor output connected to said power communications line and said sensor for outputting signals from said sensor to said power communications line; and a master microcontroller input connected to said master microcontroller for receiving said signals from said power communications line.

15. A circuit arrangement for an active traffic environment sensor comprising: a master microcontroller; an ultrasonic sensor configured for active traffic environment sensing having a communications port and a sensor power line; a power source; a microcontroller power line connected between said power source and said master microcontroller; a power communications line connected between said power source, said master microcontroller, and said ultrasonic sensor, wherein said sensor power line branches off of said power communications line; a capacitor on said sensor power line; a diode positioned between said capacitor and said power communications line; a low impedance line connected to said power source, said low impedance line having a resistor formed thereon; a high impedance line connected to said power source having a resistor formed thereon, wherein said resistor of said high impedance line has a greater resistivity than the resistor of said low impedance line; an impedance switch located on said low impedance line and configured to receive a control signal from said master microcontroller, wherein said master microcontroller controls the flow of power through said low impedance line; a master microcontroller output connected to said master microcontroller and said power communications line; a slave sensor input connected to said sensor and said power communications line, wherein said slave sensor input receives signals generated from said master microcontroller through said master microcontroller output, wherein said power communications line is used to carry said signal from said master microcontroller output to said slave sensor input; a slave sensor output connected to said power communications line and said sensor; a master microcontroller input connected to said power communications line and said master microcontroller, wherein a signal generated from said sensor through said slave sensor output is carried through said power communications line to said master microcontroller input allowing said signal to be transmitted to said master microcontroller.

16. The circuit arrangement for an active traffic environment sensor of claim 15, further comprising a master microcontroller output switch for controlling the transmission of a signal from said master microcontroller output and a slave sensor switch connected to said slave sensor output for controlling the transmission of a signal from said sensor.

17. An ultrasonic sensor comprising: an ultrasonic sensor capable of sending and receiving sound waves for detecting an object; a master microcontroller for commanding said sensor operations and for gathering and analyzing signals received from said sensor; a power source; a master microcontroller power line connected to said power source; and a power communications line connected between said power source, said sensor, and said master microcontroller, wherein said power communications line receives power from said power source and a communications signal from said master microcontroller or said sensor.

18. The ultrasonic sensor of claim 17, further comprising a diode separating said power communications line from a sensor power line wherein said diode allows power to flow from said power communications line to said sensor power line; a capacitor positioned between said diode and said sensor, wherein said capacitor stores and emits power when power being received from said power communications line drops below a predetermined value.

19. The ultrasonic sensor of claim 18, wherein said communications signal has a value of 0 or 1 , wherein when said communication signal value is

1 , a pulse at power source level is transmitted across said power communications line for about 100 μs and when said communications signal value is 0, a signal is transmitted through said power communications line at power source level for about 50 μs.

20. A traffic environment sensing arrangement comprising: a vehicle having one or more body panels; a power source; a plurality of ultrasonic sensors, each having a communications port and a sensor power line operably connected to said power source, wherein said plurality of ultrasonic sensors each further comprise: a master microcontroller; a microcontroller power line connected between said power source and said master microcontroller; a power communications line connected between said power source, said master microcontroller, and each of said plurality of sensors, wherein said sensor power line branches off of said power communications line; a capacitor on said sensor power line; and a diode positioned between said capacitor and said power communications line.

21. The traffic environment sensing arrangement of claim 20, further comprising: a low impedance line connected to said power source, said low impedance line having a resistor formed thereon; and a high impedance line connected to said power source having a resistor formed thereon, wherein said resistor of said high impedance line has a greater resistivity than said resistor of said low impedance line.

22. The traffic environment sensing arrangement of claim 21 , further comprising: a master controller output connected to said master controller and said power communications line; a slave sensor input connected to said sensor and said power communications line, wherein said slave sensor input receives signals generated from said master microcontroller through said master microcontroller output, wherein said power communications line is used to carry said signal from said master microcontroller output to said slave sensor input; a slave sensor output connected to said power communications line and said sensor; and a master microcontroller input connected to said power communications line and said master microcontroller, wherein a signal generated from said sensor through said slave sensory output is carried through said power communications line to said master microcontroller input allowing said signal to be transmitted to said master microcontroller.

23. The traffic environment sensing arrangement of claim 22, further comprising a master microcontroller output switch for controlling the transmission of the signal from said master microcontroller output and a slave sensor switch connected to said slave sensor output for controlling the transmission of a signal from said sensor.

24. The traffic environment sensing arrangement of claim 20, wherein said plurality of ultrasonic sensor are digital traffic environment sensors.