JPH0571886B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to an angle sensor that detects the angle of rotating parts of various machines. This invention relates to a detection device.

[Background of the invention]

Angle sensors are used to detect the angles of rotating parts of various machines, and the machines are controlled based on the detected values of the angle sensors. for example,
A hydraulic excavator, which is a construction machine, has a link mechanism consisting of a boom, an arm, and a bucket.The relative angle of each is detected by an angle sensor, and the control device performs the necessary calculations and control based on this detected value. Control is performed to draw a desired excavation trajectory on the tip of the bucket.

By the way, in such control based on the detected value of the angle sensor, it is clear that if a failure occurs in the angle sensor, the desired control cannot be performed. If the desired control is not carried out, the machine being controlled will move unexpectedly, which is extremely dangerous. Therefore, the control device is generally equipped with a failure determination function, and when the machine moves in a manner different from the command, it is determined that there is a failure and the machine is automatically stopped.

However, such means only determine that a failure has occurred within the control system, and it is not possible to determine whether the failure is a failure of the angle sensor, a failure of the controller, or a failure of another location. It was impossible to tell which one was there. Furthermore, in the case of a control system equipped with a plurality of angle sensors, as in the example of controlling a hydraulic excavator, it is completely impossible to determine which angle sensor has failed. Furthermore, even if a certain angle sensor fails, if the degree of influence on the final control result of that angle sensor is small, the difference between the machine movement and the command may not be determined as a failure. There was a fear that inaccurate or incomplete operations would continue.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to solve the above-mentioned conventional problems and, in particular, to prevent the occurrence of failures in which the detected values of the angle sensor become temporally discontinuous. An object of the present invention is to provide a failure detection device for an angle sensor that can reliably and easily detect failures.

[Summary of the invention]

In order to achieve the above object, the present invention provides an angle sensor that detects the rotation angle of a rotation mechanism, including a calculation means for calculating the amount of change per unit time in the output of the angle sensor, and a a setting means for setting the amount of change per unit time in the output of the angle sensor when the angle sensor is displaced at a speed; and a comparison means for comparing the amount of change calculated by the calculation means and the amount of change set in the setting means. and output means for outputting a failure signal when the amount of change calculated by the calculation means exceeds the amount of change set in the setting means.

When the angle sensor is in a normal state, the amount of change (rate of change) in the output of the angle sensor per unit time
is less than or equal to the amount of change (maximum rate of change) of the output of the angle sensor per unit time when the rotation mechanism is displaced at the maximum speed.

On the other hand, if a failure such as poor contact occurs in the angle sensor and the detected value becomes discontinuous over time, the rate of change of the angle sensor's detected value will exceed the maximum rate of change. , whereby the above-mentioned failure of the angle sensor can be detected.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a block diagram of an angle sensor failure detection apparatus according to an embodiment of the present invention. In the figure, 1A is a first member that constitutes a rotation mechanism, 1B is a second member that constitutes a rotation mechanism, and the first member 1A and the second member 1B are rotatable by a shaft. connected. In the example of a hydraulic excavator, the first member 1A corresponds to, for example, a boom, and the second member 1B corresponds to an arm. Reference numeral 2 denotes an angle sensor that is provided at the connecting portion between the first member 1A and the second member 1B and detects the relative angle between them. The angle sensor 2 is
A signal s corresponding to the detected angle is output. Reference numeral 3 denotes an arithmetic device comprised of a microcomputer, etc., which inputs the signal s from the angle sensor 2 and performs desired calculations and control based on the signal s. As a result of the calculation device 3 performing the desired calculation and control, the angle sensor 2
When it is determined that there is a failure, the arithmetic unit 3 outputs a failure signal e. Reference numeral 4 denotes a failure alarm device which is activated by inputting a failure signal e to warn of a failure of the angle sensor 2.

Next, the principle of failure determination of the angle sensor 2 in the arithmetic unit 3 will be explained based on the graph shown in FIG. In FIG. 2, the horizontal axis represents the rotational angular velocity θ· of the input shaft of the angle sensor 2, and the vertical axis represents the change in output value Δs of the angle sensor 2 per unit time ΔT. The following explanation will be given assuming that the angle sensor 2 outputs a value proportional to the rotation angle of its input shaft. Both the first member 1A and the second member 1B are rotated by the drive device of the rotation mechanism to which they belong. Therefore, the maximum value of the rotational angular velocity of the first member 1A and the second member 1B is determined by the capacity of the drive device, and naturally the relative maximum rotation of the first member 1A and the second member 1B The angular velocity θ· _nax is also determined by the capacity of the drive device.
To explain this using the example of the hydraulic excavator,
The maximum driving speed of the boom cylinder and arm cylinder is determined based on the rotational speed of the installed engine and the discharge amount of pressure oil per rotation of the hydraulic pump rotated by this engine. 1 member 1A, second member 1
The respective maximum rotational angular velocities are determined based on the various dimensions of B, and therefore the relative maximum rotational angular velocity θ· _nax is also determined.

As mentioned earlier, the output of the angle sensor 2 is
Since the value is proportional to the rotation angle of the input shaft, the value Δs of the change in the output of the angle sensor 2 per unit time ΔT is proportional to the rotational angular velocity θ of the input shaft, and the relationship between the two is As shown in Figure 2, it becomes a straight line. Then, a value Δs (this value is expressed as P) corresponding to the maximum rotational angular velocity θ· _nax is also determined. In other words, no matter how the first member 1A and the second member 1B move, the value Δs of the change in the output s of the angle sensor 2 never exceeds the maximum value P.

By the way, if a failure occurs in the angle sensor 2, the rotation angle of the input shaft and the output s will no longer be proportional, and as a result, the value Δs may exceed the maximum value P. For example, if the angle sensor 2 is composed of a potentiometer and a failure occurs due to poor contact between the resistor in the potentiometer and the slider that comes into contact with it,
Even if the input shaft rotates and the slider moves, the angle sensor 2 will output values that jump intermittently, and the change value Δs of the signal s per unit time ΔT will be the maximum value P. A situation that exceeds the above occurs. As described above, this embodiment attempts to detect a failure in which the detected values are discontinuous in time, and the difference between the value Δs and the maximum value P is constantly monitored, and the difference between the value Δs and the maximum value P is detected. When the value is greater than or equal to the value P, a failure signal e is output to warn of a failure.

Next, the operation of this embodiment will be explained with reference to the flowchart shown in FIG. When starting the device,
First, the arithmetic unit 3 receives the output signal s of the angle sensor 2.
will be incorporated. This value is represented by the symbol s1. At the same time, the timer T built in the arithmetic unit 3 becomes 0.
(step _S1 ). Then, the output signal s of the angle sensor 2 is taken in again (step S ₂ ).
This value is denoted by the symbol s2. Next, the code s2
The value of the sign s1 is calculated from the value of , and its deviation Δs is obtained (step S ₃ ). In this case, since step S ₂ is executed immediately after the processed value of step S ₁ , both values are approximately equal, and the value Δs is approximately 0. This value Δs is compared with the maximum value P described above (step S ₄ ), and since Δs<P, the process moves to step S ₅ . In step _S5 , the code of the value of code s2 is changed to code s1. Next, it is determined whether the value of the timer T has reached the above unit time ΔT (step S ₆ ), and when the value of the timer T has reached the unit time ΔT,
The value of this timer T is reset to 0 (step _S7 ),
Returning to step _S2 again, the signal s from the angle sensor 2 is received. The signal s taken in at this time is the value after a unit time ΔT has elapsed since the previous step _S2 was executed. Add the code s2 to this value (step S ₂ ),
Step _S3 is then executed to obtain the value Δs. This value Δs
is the change in the output value s per unit time ΔT, that is, the rate of change. After that, steps S ₂ to S ₇ are repeated,
In step _S4 , if it is determined that the value Δs is greater than or equal to the maximum value P, a failure signal e is output (step _S8 ).
The failure alarm device 4 is activated by the output of the failure signal e, and a failure of the angle sensor 2 is alerted.

The functions of the above arithmetic device are shown in FIG. In Fig. 4, 2 is the same angle sensor as shown in Fig. 1;
is the same fault alarm device as shown in FIG.
31 is a calculation means for inputting the detected angle from the angle sensor 2 every unit time ΔT and calculating the amount of change;
2 is a setting means for setting the amount of change per unit time of the normal angle sensor when the first member 1A and the second member 1B are displaced at the maximum speed;
The comparison means 33 compares the amount of change calculated in step 1 with the amount of change set in the setting means 32. As a result of this comparison, if the amount of change calculated by the calculation means 31 exceeds the amount of change set in the setting means 32, a failure signal is outputted from the output means 34 to the failure alarm device 4.

By the way, conventional failure detection for various sensors usually involves defining the operating range of the sensor, and determining that the sensor is abnormal when the detected value of the sensor exceeds the upper or lower limit of the operating range. It's summery. However, such means cannot detect failures within the sensor's operating range, such as poor contact in sensors using potentiometers, and incorrect detection values may be output even within the sensor's operating range. This may pose a danger to machines and devices whose drive is controlled based on the detected value of the sensor.

In contrast, in this embodiment, the maximum rate of change in the output of the angle sensor corresponding to the maximum value of the rotational angular velocity of the input shaft of the angle sensor determined by the rotation mechanism as described above, and the output of the angle sensor are determined. The obtained rate of change is compared, and when the latter is greater than or equal to the former, a failure signal is output, the failure alarm device is activated, and an alarm is issued, so even if the angle sensor does not perform detection within the above operating range. Even if the angle sensor is not continuous, it is possible to reliably and easily detect a failure of the angle sensor in which the detected value becomes temporally discontinuous, thereby ensuring the accurate operation and safety of the machine.

In addition, in the description of the above embodiment, an example was explained in which the rotation angle of the input shaft of the angle sensor and the output are proportional, but it is not necessarily limited to such an angle sensor, and even an angle sensor that is not proportional can be used. This can be applied by finding the maximum value (P) for the part where the rate of output change is maximum in that characteristic.
Further, even if there is not one angle sensor but a plurality of angle sensors to be detected, the failure can be detected by sequentially inputting the detected values to the arithmetic unit. Furthermore, instead of the fault warning device, a fault indicating device or an emergency stop device can be used, or any of these devices can be used together. Furthermore, using a fault display device,
It is also possible to centrally monitor failures of multiple angle sensors at one location.

〔Effect of the invention〕

As described above, in the present invention, the maximum rate of change in the output of the angle sensor is determined by the rotation mechanism, and a failure signal is output when the rate of change in the output of the angle sensor exceeds the maximum rate of change. As a result, even if the angle sensor is performing detection within its normal operating range, it is possible to reliably and easily detect failures in the angle sensor where the detected values are discontinuous over time. In turn, it is possible to ensure the correct operation of the machine and its safety.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a failure detection device for an angle sensor according to an embodiment of the present invention, and FIG. 2 is a characteristic diagram of the output change rate with respect to the rotational angular velocity of the input shaft of the angle sensor.
3 is a flowchart explaining the operation of the arithmetic device shown in FIG. 1, and FIG. 4 is a block diagram showing the functions of the arithmetic device shown in FIG. 1. 1A...first member, 1B...second member, 2
... Angle sensor, 3 ... Arithmetic device, 4 ... Failure alarm device.

Claims (1)

[Claims] 1. In an angle sensor that detects the rotation angle of a rotation mechanism, a calculation means for calculating the amount of change in the output of the angle sensor per unit time, and an output of the angle sensor when the rotation mechanism is displaced at a maximum speed. a setting means for setting the amount of change per unit time of , a comparison means for comparing the amount of change calculated by the calculation means with the amount of change set in the setting means, and the amount of change calculated by the calculation means. and output means for outputting a failure signal when the amount of change exceeds the amount of change set in the setting means.