The present invention is an industrial machine that can detect a position and a posture of a working implement of the industrial machine with respect to the industrial machine main unit. For instance, the present invention relates to a construction machine such as bulldozer, power shovel, etc. In particular, the invention relates to a construction machine, in which it is possible to detect the position and the posture of the construction working implement such as soil-pushing blade, bucket, etc. with respect to a construction machine main unit.
In civil engineering operation, e.g. in ground-leveling operation by using bulldozer, it is indispensable to accurately identify the position and the posture (such as tilting) of a ground-leveling implement (bulldozer blade) with respect to a ground surface to be leveled for the purpose of accomplishing the ground-leveling operation with high accuracy. Also, it is essential to accurately detect the position and the posture (such as tilting) of the ground-leveling implement for the purpose of carrying out the ground-leveling operation as initially planned without depending on a sense of an operator of the construction machine.
In the past, a construction machine for detecting height and position of the ground-leveling implement has been known and disclosed in JP-A-2005-337741.
FIG. 6 of JP-A-2005-337741 shows a rotary laser irradiation unit 1 for projecting a laser beam 5 in rotary irradiation and for forming a reference plane. FIG. 6 also shows a pole 3 erected on a ground-leveling implement 2, and a photodetecting unit 4 mounted on the pole 3. It has been practiced in the past to detect the laser beam 5 by the photodetecting unit 4, to detect the reference plane, and to detect a position in a vertical direction of the ground-leveling implement 2 based on a position of the reference plane detected by the photodetecting unit 4.
According to JP-A-2005-337741, it is possible to detect a position of the ground-leveling implement 2 with respect to the reference plane, i.e. the ground surface to be leveled, while it is not possible to detect the position and the posture of the ground-leveling implement 2 with respect to a construction machine main unit 6. On the other hand, when an operator operates the ground-leveling implement 2, the operator must adjust position and posture (such as tilting) of the ground-leveling implement 2 with reference to the construction machine main unit 6. In this case, adjusting operation based on an obtained result of detection may not necessarily be consistent with the sense of the operator and may cause an erroneous operation.
Further, U.S. Pat. No. 7,317,977 B2 discloses a bulldozer 7 as a construction machine. A pole 9 is erected on a blade 8 of the bulldozer 7, a first GPS antenna 11 is installed at an upper end of the pole 9, and a second GPS antenna 12 and a third GPS antenna 13 are installed in front and back on the bulldozer 7 itself.
According to the U.S. Pat. No. 7,317,977 B2, as shown in FIG. 7, an absolute position in upward direction of the blade 8 can be detected by the first GPS antenna 11, and a position and a direction of the bulldozer 7 can be detected by the second GPS antenna 12 and the third GPS antenna 13. Based on a result of the position detection by the first GPS antenna, and based on the result of the position detection by the second GPS antenna 12, and the third GPS antenna 13, a relative position of the blade 8 with respect to the bulldozer 7 can be determined by a calculation.
However, a position detecting system including the GPS antenna is expensive in cost. Further, three sets of the systems are needed for determining the relative position of the blade, accordingly, the system is so expensive.
When the blade 8 is tilted in a front-to-back direction, the pole 9 is also tilted. As a result, a deviation occurs between a horizontal position and a vertical position detected by the first GPS antenna 11 and an actual position of the blade 8. Also, in case where the blade 8 is rotated in horizontal direction around the pole 9 as a center, there is no change in a result of the detection by the first GPS antenna 11, and a rotating position in horizontal direction of the blade 8 cannot be detected.
Further, in some cases, the tilting of the blade 8 with respect to the bulldozer 7 is detected by using a tilt sensor. In such case, a responsiveness of the tilt sensor is not be very accurate, and a reaction to vibration may occur. As a result, the tilt sensor is not very suitable for the detection of tilting of the blade 8 when the blade 8 is moving.