TECHNICAL FIELD
Remote Control for moving toys
BACKGROUND
There are various methods to remote control moving toys. The most common method applies a handheld unit (‘RCU’) configured to be manipulated by user's hands and transmit respective movement commands to the toy by Infra-Red (‘I/R’) or Radio coded signals. The moving toy includes a circuitry configured to receive these coded signals, decode the commands and activate the toys' motors in respect of such commands.
The main disadvantage of this method is that the movement commands relate to the momentary orientation of the toy, and not the user. If the toy is facing away from the user—a ‘turn right’ command will cause the toy to turn its right which is also user's right side. But if the toy is facing the user—then same command will also cause the toy to turn to its right, but this time it is ‘left’ for the user. This is known as the ‘reversing effect’, and this makes the directional control of the toy to be not intuitive anymore when the toy changes often its direction. In fact, it makes this method of remote control to be impractical for younger and non-experienced users.
To overcome this disadvantage, a remote control by light has been introduced. U.S. Pat. No. 3,406,481 describes a ‘light following’ moving toy which moves in the direction of a modulated light beam source. The toy makes use of at least two photoconductive cells laterally spaced on the toy and an electronic circuit both configured to determine and move towards the direction of the light beam source.
An alternative method is introduced in U.S. Pat. No. 7,147,535 ('535). The remote control projects a spot on the ground and the toy, equipped with optical sensors, follows the spot. This overcomes the ‘reversing effect’.
However, the method described and claimed in this patent is analogue and inherently limited because the analogue electronic circuit is configured to drive the motors in a speed that is substantially proportional to the sum of the intensity of the flows of the modulated light received by the sensors, and wherein the difference in the intensity of same controls its steering. Some examples of the limitations:—
- a. When there is no light spot, then the electronic circuit is configured to stop the motors from moving altogether. Stopping the motors of a ground vehicle causes the vehicle to freeze in place waiting for the next command which is fine. However, this is not workable for a flying toy, as stopping the motors in midair causes the toy to fall and crash.
- b. In ground vehicles, the speed of the motors is proportional to speed of the vehicle. Whereas in helicopters and other flying toys the speed of the motors is proportional to the acceleration, and not to the speed, of the helicopter. This is a fundamental difference. As such the method of '535 in which the speed of the motors is substantially proportional to the intensity of the flow of the modulated light received—is not workable for remote control of helicopters.
- c. Patent '535 provides that the speed of the motors is substantially proportional to the intensity of the flow of the modulated light received. This results that toy's speed is slower when far away from the light spot and increasing when the vehicle approaches the light spot. However, this is one single pattern of speed control, and there is a need for added patterns of speed control which the method of '535 inherently cannot provide. Examples of such other speed patterns are (1) keeping same speed all the way; (2) reducing the speed of the vehicle as it approaches its target; (3) moving away (i.e. avoiding) the light spot; (4) approaching the light spot but stopping at a pre-determined distance away, etc.
The method described in this patent provides for an advanced light remote control method for toys which overcomes '535 limitations for the ground toys, and more important—provides first solution for light remote control of helicopters.
SUMMARY OF INVENTION
The exemplary embodiment in FIG. 1 comprises a toy helicopter, fitted with four directional Infra-Red (‘I/R’) sensors laterally placed in the front of the helicopter, one sensor 11 looking forwards and up at about 45 degrees, second sensor 12 looking forwards and down at same angle, third sensor 13 looking horizontally at 45 degrees to the right and fourth sensor 14 looking horizontally at 45 degrees to the left.
The sensors directions are configured so that when the hovering helicopter 21 in FIG. 2 faces wall 22, and an I/R light beam makes a spot 23 on the wall in front of the helicopter, the signal intensity received by each sensor relative to the intensity at other sensors will be as follows:
- a. If the I/R spot is on top left side of front of helicopter as shown in FIG. 2 then the signal in sensor 11 will be stronger than in 12, and 14 stronger than 13;
- b. If spot is on top right then 11 stronger than in 12, and 13 stronger than 14;
- c. If spot is on bottom right then 12 stronger than in 11, and 13 stronger than 14;
- d. If spot is on bottom right then 12 stronger than in 11, and 14 stronger than 13.
The I/R spot is created by a hand-held controller in an exemplary shape of a directional torch, which sends a directional beam of modulated I/R signal in any direction the user aims the controller at. That I/R beam signal 31 in FIG. 3 consists of a 38 KHz carrier, amplitude-modulated with the saw tooth (‘Saw-Tooth Signal’).
If the received signal 32 in one sensor is stronger than the received signal 33 in the second sensor, then the electronic output signal 35 from the first sensor will be wider than the electronic output signal 36 from the second sensor. This is a simple result of the fact that the output from the I/R sensors is binary—if the received signal intensity is above a certain level 34—then the output will be a logical ‘1’, whereas if the received signal intensity is below level 34—then the sensor output is logical ‘0’. In other words, this Saw-Tooth shaped signal provides a simple low cost method to gauge a received signal's strength, wherein the strength of the signal is converted into width of a binary signal by a common I/R sensor.
This saw-tooth method is exemplary only, and can be replaced by any other shape of amplitude-modulation shape, as well as it can be replaced by frequency modulated carrier of 38 KHz that yields similar results by making use of the internal band-pass filter of the sensors, and any other methods of gauging I/R signal intensity.
FIG. 10 depicts a pair of sensors having spread orientation. The light intensity received at sensor 101 is stronger than at 102, which results is signal width 103 to be wider than 104. The difference between the widths is proportional to the angle 106. This method of gauging the angle is applied for the pair of sensors 11 and 12, in which the angle over the horizon is so determined. At same time this method is applied with the pairs of sensors 13 and 14—determining the horizontal angle of the light spot.
The reason for using the preferred 38 KHz carrier is that the common low cost I/R sensors in the market incorporate a built-in band-pass filter which is centered around 38 KHz to eliminate background noise.
The helicopter comprises of a microcontroller (‘MCU’), main motors M1, M2 that drive main rotors R1, R2; a smaller motor MT on tail that drives small back rotor RT; an electronic gyro and a rechargeable battery BAT.
The outputs of the pair sensors 11, 12 connect to input ports IU, ID of the MCU as depicted in FIG. 4. Similarly, sensors 13, 14 connect to IR, IL. The gyro connects to input port IG. The battery BAT delivers voltage VM.
MCU output ports OP1, OP2 connect to motors M1, M2 delivering drive signals P1, P2 which are binary PWM modulated. Output ports OMF, OMB connect to motor MT with signals PF, PB configured to rotate RT clockwise or anticlockwise respectively.
The main rotors are configured to rotate in opposite directions so as to mutually offset the counter rotation of the body of the helicopter. If one rotor slightly rotates faster, then the helicopter will slightly spin in the other direction.
The speed of each rotor follows its respective motor. The speed of the motor is proportional to the voltage VM multiplied by the duty cycle of the PWM driving it which is T1 divided by T, as per FIG. 5.
This configuration provides the following:
- a. The lifting force created by each rotor is proportional to the speed of the rotation of each rotor. The force on any mass is directly proportional to the resulting acceleration of that mass. Therefore, the sum of both rotors speeds is also proportional to the upwards acceleration of the helicopter. Consequently, to cause an intentional increase in the lifting force, it is required to increase duty cycle of both P1 and P2.
- b. The yaw, or spin of the helicopter, is determined by the relative speed between the two rotors which rotate in opposite directions. Consequently, to cause an intentional spin or turn of the helicopter it is required to increase the duty cycle of P1 or P2 with simultaneous similar decrease in the duty cycle of P2 or P1 respectively.
- c. The gyro is configured to deliver a signal when the helicopter spins, and the MCU is configured to respond automatically with a slight increase of the duty cycle of P1 accompanied by a similar decrease in the speed of P2, or vice-versa, in a closed loop configuration so as to offset any residual tendency of the helicopter to spin.
The consequences of the aforesaid are:
- a. The MCU controls only the duty cycles of signals P1 and P2, while the speed of the motors depends also on voltage VM. The voltage VM drops after just a few tens of seconds of flight, because toy helicopters use relatively low capacity batteries to save costs. This means that even to keep the same speed of the motors, there is a need to increase the duty cycles of P1 and P2 from time to time.
- b. At any given speed of the motors, the helicopter may be climbing or descending at fixed or accelerated speed. Completely different than a ground vehicle in which the motors speed determines also the vehicle's speed. This requires the MCU to create a smart pattern of change of the duty cycles of P1 and P2 in response to sensors signals SU and SD.
The method of smart pattern as provided in the exemplary embodiment is hereby explained. When the I/R light spot is pointing above the helicopter level, then the I/R signal strength of sensor 11 is stronger than that of sensor 12, which is detected by the MCU as described previously. In such case the pattern described in FIG. 6 is applied. When the I/R light spot is pointing below the helicopter level, then the I/R signal strength of sensor 12 is stronger than that of sensor 11, and in such case the pattern described in FIG. 7 is applied.
In FIG. 6—PW1 and PW2 are the PWM duty cycles of signals P1 and P2 respectively. When the I/R light spot switches on and points higher than the helicopter, shown as 61, then the PWM increases by DU1. When light switches off, the PWM decreases by DU2. Note that DU2 is smaller than DU1.
In FIG. 7, when the I/R light spot switches on and points lower than the helicopter, shown as 71, then the PWM decreases by DD1. When light switches off, the PWM increases by DD2. Note that DD2 is smaller than DD1.
If the light spot is on the right/left of the helicopter, the MCU sends the signal as depicted in FIG. 8. Signal 81 shows the time in which the right I/R sensor receives a stronger signal than left I/R sensor. In such case the MCU will increase the duty cycle of P1 from P10 by DR for a short fixed duration of T1, and then return to the previous duty cycle of P10. At the same time the MCU will decrease the duty cycles of P2 from P20 by same DR, for the same short fixed duration T1.
If the right/left I/R sensor still receives a stronger signal after T, the process repeats.
The above describes the methods for UP/DOWN, and TURN RIGHT/LEFT remote control by I/R light for the helicopter. This is known as ‘2-channel’ control. For the third channel FORWARDS/BACKWARDS (and some helicopters have even a fourth channel of MOVE SIDEWAYS RIGHT/LEFT)—there is added a coded command as described in FIG. 9 part 91. Turning on the I/R light beam on the controller is by either one of three push buttons—(1) encodes ‘FWD’ command; (2) encodes ‘BWD’ command, and (3) nil. This part is decoded by the MCU of the helicopter wherein code (1) causes the tail rotor to rotate in one direction, and (2)—in the other direction. Command (3) does not affect the tail rotor.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 Position of I/R sensors on the Helicopter
FIG. 2 Light Spot on the wall and its effect
FIG. 3 Saw Tooth signal
FIG. 4 Electronic Configuration
FIG. 5 Control of Speed of each motor/rotor
FIG. 6 Light Spot pointing above the helicopter
FIG. 7 Light Spot pointing below the helicopter
FIG. 8 Light Spot pointing to the right/Left of the helicopter
FIG. 9 Encoded saw tooth signal
FIG. 10 Direction finding with 2 sensors
Patent Application
20120122367
