EP0587982A1

EP0587982A1 - Remote control system

Info

Publication number: EP0587982A1
Application number: EP93106468A
Authority: EP
Inventors: Osamu c/o SMK Corporation Yoshikawa
Original assignee: SMK Corp
Current assignee: SMK Corp
Priority date: 1992-09-14
Filing date: 1993-04-21
Publication date: 1994-03-23
Also published as: JPH07112302B2; JPH0698383A

Abstract

A remote control system has a transmitter and a receiver. The transmitter collects command data, combines it with an identification code into frames, and transmits the frames at random intervals. The receiver passes the data if the identification code is recognized. If the code is not recognized due to an incorrect source or a collision, the data is rejected. When several of these units are in operation simultaneously, the random waiting periods between frames ensure that data reaches the receivers without colliding with other signals. The receiver which recognizes the proper identification code passes the data to its main body, while the remaining receivers reject it.

Description

The present invention relates to remote control system, and more specifically, to a remote control system which avoids the signal interference generated when several remote control systems are operated at the same time.
Remote control systems generally include a remote transmitter, a receiver incorporated into a main system, and a communication link therebetween. In the transmitter, command signals are processed, modulated, and transmitted over a communication link, usually wire, acoustic or electromagnetic radiation (e.g. RF waves, infrared, sound waves and the like). The transmission is received by the receiver unit and demodulated. Command data is extracted and relayed to the main system.
It is convenient to impose a plurality of signals, originating in different transmitters, on a single channel to the receiver unit. Interference between the transmitted signals limits the usefulness of this technique.
Under the prior art, data streams of 16 or 32 bits per frame organized by a PAM-PPM process are transmitted at predetermined intervals. This transmission method is useful in an environment in which only a single remote control system is employed, or one in which several remote control systems are used at different times.
A drawback of the prior art is that several remote systems cannot operate simultaneously. If the systems maintain identical carrier frequencies and periods between transmissions for acoustic or RF systems, or identical pulse patterns for an infrared system, the data within those transmissions collide. Both signals become jumbled and are unrecognizable to the receiving systems.
Conventional methods employed to solve the above drawback include multiple frequency and poling methods. In the multiple frequency method, a different frequency is used for each respective sender-receiver system. In the poling method, a bidirectional remote system utilizes protocol control.
A drawback of these conventional methods is that they require complicated circuit and control mechanisms, resulting in bulkier devices and higher costs.
Accordingly, one object of the invention is to provide a remote control system which overcomes the drawbacks of the prior art. Further object of the invention is to provide a remote control system in which several remote units can effectively employ a common carrier frequency simultaneously.
The present invention includes a remote control transmitter having an operating device, a first control device, and a transmitter. The operating device gathers command data and passes it to the first control device. The first control device combines the command data and a predetermined ID code, which is unique to each transmitter, into frames. These frames are then transmitted by a transmission unit to a remote control receiver attached to a main body.
Once a frame is dispatched, the first operating device selects a random number, preferably from a look-up table. This number is fed to a counter which down-counts to zero. A subsequent frame will not be transmitted until the counter reaches zero. As the counter down-counts from a random number, the "waiting period" between frames has a random length.
The transmitted frame is received by a sensor of the remote control receiver. The frame is demodulated and analyzed by a second control device. If the second control device recognizes the identification code as originating from its assigned remote control transmitter, then the command data is passed to the main body. If the identification code is not recognized (e.g., produced from a source other than the assigned transmitter, result of a collision with another signal, etc.), the data is rejected, and the system waits for the receipt of a correct identification code.
The above system works in concert with several units as follows. Several transmitter operate simultaneously, thereby emitting frames which are spaced apart by a random waiting period. The random nature of the pulses ensures that while some pulses will collide, others will be received without impediment. The signal is detected by each of the receivers, but only the receiver(s) which recognize the proper identification code will pass the data to its main body, while the other receivers reject it.
The above system can also function with less receivers than transmitters, provided that the receivers can discern between the individual identification codes.
According to an embodiment of the present invention, there is provided a remote control system for a main body device, comprising means for transmitting a signal, said means for transmitting having an identification code, means for generating a random number, said signal including a plurality of frames, said frame including said identification code and data, means for producing a waiting period between successive ones of said plurality of frames, said waiting period having a length related to said random number, means for receiving said signal, said means for receiving including means for recognizing said identification code, and said means for receiving including means for passing said data to said main body device responsive to said means for recognizing.
According to a further embodiment of the invention, there is provided a remote control system, comprising at least first and second means for transmitting a signal, each of said at least first and second means for transmitting including means for generating a random number and a identification code, respectively, means in each of said at least first and second means for transmitting for producing a waiting period having a random length responsive to their respective random numbers, said signal including a plurality of frames, said plurality of frames including said unique identification code and data, successive ones of said plurality of frames being separated by said waiting period, at least one means for receiving said signal from said at least first and second means for transmitting, each of said at least one means for receiving including means for recognizing said identification code of the least one of said at least first and second means for transmitting, and said at least one means for receiving including means for passing said data to an assigned main body only when recognized by said means for recognizing.
According to a still further embodiment of the invention, there is provided a remote control system for a main body, comprising as transmitter for transmitting a signal, said transmitter having a unique identification code, said signal including a plurality of frames, each of said plurality of frames including said identification code and data, a first operation means connected to a means for inputting said signal, and said first operating means including means for imposing waiting periods having a random lengths between successive ones of said plurality of frames.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.

Fig. 1 is a schematic view of a remote control system of the present invention;
Fig. 2 is a flow chart describing the operation of the remote control transmitter;
Fig. 3(a) is a timing chart of signal transmission of the present invention;
Fig. 3(b) is an expanded view of a data pulse Ta₁ of Fig. 3(a); and
Fig. 4(a)-(f) are timing diagrams of a plurality of transmitted signals.

Referring now to Fig. 1, a remote control system 100 includes a remote control transmitter 1, a main body 2, and a remote control receiver 3. Remote control transmitter 1 includes an operating device 5, a first control device 6 (preferably a microcomputer), and a transmitter 7. Remote control receiver 3 includes a sensor 8, demodulator 9, and a second control device 10 (preferably a microcomputer). Input signals are generated at operating device 5 and organized by first control device 6 into frames. Each frame contains an identification code followed by command data for main body 2. The frames are dispatched a sensor 9 by transmitter 7 over a communication link media 4, usually infrared or radio emissions or the like.
In one embodiment of the invention, each transmitter 1 has a corresponding transmitter 3. A typical example of this embodiment would be several radio controlled model cars being used in the same area.
In another embodiment of the invention, several transmitters 1 transmit to a lesser number of receivers 3. Each receiver 3 can either be connected to a single main body 2 which processes the signals independently (e.g. a video game with two joysticks), or can act as a relay station for several main bodies.
In a still further embodiment of the invention, the number of receivers exceeds the number of transmitters. Such a case could exist in situations in which a single transmitter 1 controlled more than one main body 2.
In each of the above embodiments, it is essential to ensure that signals send by transmitter 1 is received clearly by an assigned main body 2. The present invention accomplishes this by (1) continually varying the period between transmitted signals based on a random number and (2) assigning an identification code to each frame which can only be recognized by the pre-selected receivers 3, which will only pass the signal if the signal is recognized.
Referring now to Figs. 2 and 3(b), first control device 6 operates as follows. At a step 21, data is collected and organized into transmission frames 30. Each frame includes an identification code and command data obtained from operating device 5. The identification code is unique to each remote control transmitter 1, and will only be recognized by an assigned receiver 3.
At a step 22, a look-up table random number generator produces a random number. This number is input to a timer at a step 23. The timer begins down-counting from the random number at a step 24. At a step 25, the timer is checked. If the count has reached zero, the data frame is transmitted at a step 26, and the cycle begins anew. If not, down-counting continues at step 24. The period between concurrent signals produced by the down-counting is known as the "waiting period".
Referring again to Fig. 1, the transmitted frame is received at sensor 8 and demodulated at demodulator 9. The demodulated signal is then passed to second control device 10, which determines if the proper ID code is present in the frame. If the receiver does not recognize the proper identification code, it rejects the command data as either transmitted from another source or the result of a collision. If the code is recognized, the data frame is accepted and passed to a main body 2.
Referring now to Fig. 3(a), a series of frames Ta₁ - Ta₄, each having a fixed length and containing an identification code and command data, are separated by random waiting periods, Tb₁ - Tb₄, respectively. The length of each waiting period varies based on the random number assigned to the timer of first control device 6 at step 24.
Referring now to Figs. 4(a)-(f), first, second, third and fourth remote control transmitters S1, S2, S3 and S4 each transmit a series of sending signals 31, 32, 33 and 34, respectively. Each individual signal is separated by a random waiting period established by first control device 6 of each sender.
In one embodiment of the invention, these signals are received by first, second third and fourth receivers, which are connected to first, second, third and fourth main bodies respectively, along the points in time indicated in Fig. 4(e). A common application of such a system would be several radio controlled cars or planes operating within the same broadcasting area.
At time t1, sending signals 31, 32, 33 and 34 collide. The resulting jumbled signal is rejected by each receiver as unrecognizable.
At time t2, signal 32 is transmitted without collision and received by each receiver. Recognizing a corresponding identification code, the second receiver passes the command data to the second main body. The first, third and fourth receivers reject the data for failure to recognize a proper identification code. In this manner, only the second main body reacts to signal 32.
Similar outcomes are realized at times t2, t3, t4, t6, and t8, in which non-overlapped signals are transmitted and received by each receiver, but only passed by the corresponding receiver unit to the corresponding main body.
At time t5, signals 32 and 34 are transmitted simultaneously. Both signals collide, rendering them unrecognizable to the second and fourth receivers. The same result occurs at time t7, when signals 31, 33 and 34 overlap.
In another embodiment of the invention, signals 31, 32, 33, and 34 are sent to at least one receiver, each of which is connected to at least one main body. Each of these receivers would be capable of differentiating between several identification codes, thereby passing data only to the assigned main body. An example of this embodiment would be a home video game with multiple joysticks which transmit to a single receiver.
By utilizing the above system, several remote control systems can be employed simultaneously using only a single carrier frequency. A remote control unit can thus be produced which is smaller and cheaper than the prior art.

Example:

The above described invention was utilized in an experiment which employed four pairs of sender-receivers at the same time. Random number were obtained from a look-up table consisting of 6 and 9. The results were as follows:

No. X1 X2 X3 X4 X5 Average waiting time Maximum waiting time

1 6 6 6 6 6 24.9 66

2 9 6 6 6 6 29.5 66

3 9 6 9 6 6 34.5 72

4 9 9 9 9 9 53.1 72
Units for Table 1 consist of Ta, where Ta is the length of the fixed data frame. Thus if X1 = 6, then X1 is six times the length of a fixed frame. In practical terms, if Ta = 10ms, X1 = 6*Ta = 60ms.
An average waiting period is defined as the average time between the receipt by a receiver of subsequent non-overlapped signals from a corresponding sender. The maximum waiting period is defined as the maximum amount of time between the receipt by a receiver of subsequent non-overlapping signals from a corresponding sender. For example, the maximum waiting time for receiver No. 4 to receive a clear signal from sender No. 4 for a Ta = 10ms would be 72*Ta = 720ms.
The above invention is not limited to an infrared carrier media. As would be recognized by one skilled in the art, any appropriate type of transmission media could be employed, including RF signals, sound waves, a bus-type wire system, or the like.

Claims

A remote control system for a main body device, comprising:
means for transmitting a signal, which having an identification code, said signal including a plurality of frames, and said frame including said identification code and data;
means for generating a random number;
means for producing a waiting period between successive ones of said plurality of frames, said waiting period having a length related to said random number; and
means for receiving said signal, which including means for recognizing said identification code and means for passing said data to said main body device responsive to said means for recognizing.
A remote control system according to claim 1, wherein said means for receiving includes means for rejecting said command data if more than one of said frames is detected at a point in time.
A remote control system according to claim 1 or 2, wherein said length of said waiting period is sufficient to allow said signal to reach said means for receiving without interference from other broadcasting sources.
A remote control system, comprising:
at least a first and a second means for transmitting a signal, each of which including means for generating a random number and a identification code, and means for producing a waiting period having a random length responsive to their respective random numbers, wherein said signal including a plurality of frames, said frames including said unique identification code and data, and successive ones of said frames being separated by said waiting period; and
at least one means for receiving said signal from said means for transmitting, each of which including means for recognizing said identification code of at least one of said means for transmitting, and means for passing said data to an assigned main body only when recognized by said means for recognizing.
A remote control system according to claim 4, further comprising: a number of said means for transmitting and said means for receiving being equal; and each of said means for receiving including means for recognizing only said unique identification code of each of said means for transmitting respectively.
A remote control system according to claim 4 or 5, wherein said means for transmitting have identical carrier frequencies.
A remote control system according to claim 4, 5, or 6, wherein said means for transmitting further comprises: a counter for down-counting from said random number; and means for allowing a subsequent one of said at least one frame to be transmitted when said counter reaches zero.
A remote control system according to claim 7, wherein said waiting period is defined by the time elapsed by said counter during down-counting to zero.
A remote control system according to claim 7 or 8, wherein said means for generating a random number includes a look-up table.
A remote control system for a main body, comprising:
a transmitter for transmitting a signal, which having a unique identification code, said signal including a plurality of frames, and each of said plurality of frames including said identification code and data; and
a first operating means connected to a means for inputting said signal, which including means for imposing waiting periods having a random lengths between successive ones of said plurality of frames.
A remote control system according to claim 10, further comprising: a receiver including a sensor, a demodulator and a second operating means, wherein said second operating means including means for recognizing said identification code, and means for passing said command data to said main body responsive to said means for recognizing.
A remote control system according to claim 10 or 11, wherein said means for imposing further comprises: means for generating a random number; a counter which is effective for down-counting from said random number; and means for allowing a subsequent one of said plurality of frames to be transmitted when said counter reaches zero.
A remote control system according to claim 12, wherein said waiting period is defined by the time elapsed by said counter during down-counting to zero.
A remote control system according to claim 12 or 13, wherein said means for generating a random number includes a look-up table.