Geometrical instruments – Straight-line light ray type – Level
Reexamination Certificate
2002-03-27
2003-08-12
Bennett, G. Bradley (Department: 2859)
Geometrical instruments
Straight-line light ray type
Level
C033S0010PT, C033S282000
Reexamination Certificate
active
06604293
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of the following priority application is herein incorporated by reference:
Japanese Patent Application No. 2001-095917 filed Mar. 29, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surveying instrument and a method for drive control thereof which rotationally drive a surveying optical system to be oriented toward a surveying target with a motor or the like.
2. Description of Related Art
There is a technology for rotationally driving a surveying optical system provided in a surveying instrument with a motor in the known art. For instance, Japanese Laid-Open Patent Publication No. H 4-163608 discloses a technology for controlling the motor rotation based upon a detection output from an encoder provided to detect the rotational angle of the surveying optical system which is caused to rotate by the drive motor.
While high-speed drive must be achieved in the control of the drive executed by a motor in a surveying instrument in order to orient the surveying optical system toward the target promptly, the surveying instrument also must be capable of implementing low-speed drive in order to be able to stop the surveying optical system in accurate alignment with the target. During high-speed drive, the operator enters a rotational angle into the surveying instrument so as to rotate the surveying optical system by, for instance, 10°, and in response, the surveying instrument implements fast rotational drive so as to rotate the surveying optical system by the specified rotational angle value. During low-speed drive, on the other hand, rotational drive is implemented to set the rotational angle of the surveying optical system accurately in, for instance, 1-sec increments. A complex speed reducing mechanism similar to the transmission in an automobile is required in order to achieve drive control over a wide dynamic range from high speed to low speed.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a surveying instrument and a method for drive control thereof capable of driving a surveying optical system with a pulse motor over a wide dynamic range in response to any changes in the speed from high speed to low speed and stopping the surveying optical system when it is oriented toward the surveying target with a high degree of accuracy.
In order to achieve the object described above, a surveying instrument according to the present invention, comprises a surveying optical system to be oriented toward a surveying target, a drive motor that drives said surveying optical system, a first drive control circuit that outputs a first drive signal having a first frequency and a first pulse duty cycle and used to continuously drive said drive motor, a second drive control circuit that outputs a second drive signal having a second frequency and a second pulse duty cycle and used to drive said drive motor so as to allow said drive motor to alternate accelerations and a virtual stop, and a control device that rotationally drives said surveying optical system to set said surveying optical system at a predetermined position by first providing said first drive signal to said drive motor to drive said drive motor and then providing said second drive signal to said drive motor to drive said drive motor.
The surveying instrument may comprise an encoder circuit that outputs a signal corresponding to an extent to which said surveying optical system is driven, a goniometric calculation circuit that performs goniometric calculation by using the signal output by said encoder circuit to determine a rotational angle of said surveying optical system, and an interpolation calculation circuit that performs interpolation calculation of the rotational angle by using the signal output by said encoder circuit to determine a rotational interpolation angle, wherein said second drive control circuit changes at least one of the second pulse duty cycle and the second frequency of said second drive signal based upon the rotational angle and rotational interpolation angle determined by said goniometric calculation circuit and said interpolation calculation circuit. It is preferable that said goniometric calculation circuit and said interpolation calculation circuit perform the goniometric calculation and the interpolation calculation after said second drive control circuit first outputs said second drive signal to said drive motor and said drive motor thus rotationally driven virtually comes to a halt; and said second drive control circuit next outputs said second drive signal which reflects the rotational angle and rotational interpolation angle determined by said goniometric calculation circuit and said interpolation calculation circuit.
It is preferable that the second frequency of said second drive signal is lower than the first frequency of said first drive signal, and a second pulse width based upon the second frequency and the second pulse duty cycle is larger than a first pulse width based upon the first frequency and the first pulse duty cycle. It is desirable that said second drive control circuit sets the second frequency of said second drive signal within a 1 Hz~20 Hz range and also ensures that the second pulse width is within a 10 &mgr;sec~20 msec range.
The surveying instrument may further comprise an encoder circuit that outputs a signal corresponding to an extent to which said surveying optical system is driven, a goniometric calculation circuit that performs goniometric calculation by using the signal output by said encoder circuit to determined a rotational angle of said surveying optical system, and an interpolation calculation circuit that performs an interpolation calculation of the rotational angle by using the signal output by said encoder circuit to determine a rotational interpolation angle, wherein said first drive control circuit changes at least the first pulse duty cycle of said first drive signal based upon the rotational angle determined by said goniometric calculation circuit, and said second drive control circuit changes one of the second pulse duty cycle and the second frequency of said second drive signal based upon the rotational angle and rotational interpolation angle determined by said goniometric calculation circuit and said interpolation calculation circuit.
Said control device may select one of said first drive signal and said second drive signal to be provided to said drive motor in correspondence to the rotational angle calculated by said goniometric calculation circuit.
It is possible that the surveying instrument further comprises a speed detection device that detects a speed with which said surveying optical system is given, wherein said control device provides said first drive signal to said drive motor if the drive speed detected by said speed detection device exceeds a predetermined value and provides said second drive signal to said drive motor if the speed detected by said speed detection device is equal to or lower than the predetermined value.
In order to achieve the object described above, a surveying instrument according to the present invention, comprises a surveying optical system to be oriented toward a surveying target, a drive motor that drives said surveying optical system, a first drive control circuit that implements drive control on said drive motor at a first drive speed by outputting a first drive signal having a first frequency and a first pulse width, a second drive control circuit that implements drive control on said drive motor at a second drive speed lower than the first drive speed by outputting a second drive signal having a second frequency lower than the first frequency and a second pulse width larger than the first pulse width, and a control device that provides one of said first drive signal and said second drive signal to said drive motor. It is possible that the surveying instrument further comprised an encoder circuit that outputs a signal corresponding to an extent to which said surveying optical system is driven, a goniometric calcul
Bennett G. Bradley
Nikon Geotecs Co., Ltd.
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