Box girder bottom plate maintenance robot and maintenance method

Abstract

A box girder bottom plate maintenance robot comprises two storage areas and a robot body, the robot body comprises a mounting frame, a first connecting arm, a second connecting arm and a third connecting arm, two rows of supporting wheels are arranged in the mounting frame, the first connecting arm is fixed to the top of the mounting frame, a coil is wound around the first connecting arm, the first connecting arm is electrically connected with a power source, and a first electromagnet is formed; the horizontal section is clamped between the two rows of supporting wheels, the two vertical sections extend out of the mounting frame, are wound with coils respectively and are electrically connected with a power supply to form a second electromagnet, the third connecting arm is of an L-shaped structure, the vertical sections are arranged at the bottom of the mounting frame, the extending end of the horizontal section exceeds the projection range of the mounting frame, and a camera is arranged. The storage area comprises a belt conveying mechanism, the extending direction is perpendicular to the length direction of the box girder, and a belt of the belt conveying mechanism is flush with the bottom of the mounting frame. The device is simple in structure, low in maintenance cost and capable of effectively meeting the maintenance requirements of the box girder bottom plate.

Description

Technical Field

[0001] The present invention relates to the field of municipal bridges, and in particular to a box girder bottom plate maintenance robot and a maintenance method. Background Art

[0002] Steel box girder is a commonly used structural form for large-span bridges. It is composed of a top plate, a bottom plate, a web plate, a transverse partition, a longitudinal partition and stiffening ribs welded together to form a whole. It has the advantages of good mechanical properties, reasonable weight, convenient construction, and can be prefabricated in factories. It has a wide range of uses.

[0003] Steel box girders require regular maintenance. For the bottom plate maintenance work of steel box girders, it is usually done manually by sliding under the steel box girder and being pulled by others for maintenance. Due to the large span of the steel box girder and the long length of the lifting rope used, the height gap between the middle section of the lifting rope and the bottom of the steel box girder is large, the manual maintenance accuracy is reduced, and multiple reciprocating movements are required, which is labor-intensive and difficult to conduct reasonable inspections. In addition, the height of the steel box girder is high, and there is also a risk of falling from a high altitude.

[0004] Therefore, designing a floor maintenance robot that can replace manual labor in order to solve the above problems is an issue that needs to be urgently addressed by technical personnel in this field. Summary of the invention

[0005] One of the purposes of the present invention is to provide a box girder bottom plate maintenance robot in view of the deficiencies in the prior art, which has a simple structure and low maintenance cost and can effectively meet the maintenance needs of the box girder bottom plate.

[0006] The second purpose of the present invention is to provide a method for inspecting the bottom plate of a box girder using the above-mentioned maintenance robot, which is simple and convenient to operate, can achieve the purpose of automatic maintenance, greatly reduce the intensity of manual labor, and ensure personnel safety. In addition, it can also avoid the occurrence of detection blind spots.

[0007] The technical solution to achieve one of the purposes of the present invention is: a box girder bottom plate maintenance robot, comprising two storage areas and a robot body, a power supply is arranged in the robot body, the robot body comprises a mounting frame, a first connecting arm, a second connecting arm, and a third connecting arm, two rows of support wheels are arranged in the mounting frame, the number of support wheels in the same row is at least two, and they are located at the same height, at least one support wheel is driven to rotate by a first motor, the first connecting arm is fixed to the top of the mounting frame and extends vertically upward, a coil is wound around the first connecting arm and is electrically connected to the power supply to form a first electromagnet, the second connecting arm is in a U-shaped structure, and the horizontal section of the second connecting arm is clamped between the two rows of support wheels, The two vertical sections of the second connecting arm extend out of the mounting frame and have the same height as that of the first connecting arm. Coils are respectively wound around the two vertical sections of the second connecting arm and are electrically connected to a power source to form a second electromagnet. The third connecting arm is in an L-shaped structure. The vertical section of the third connecting arm is disposed at the bottom of the mounting frame and is driven to rotate by a second motor. The extending end of the horizontal section of the third connecting arm exceeds the projection range of the mounting frame and is provided with a camera. The storage area includes a belt conveyor mechanism. The two belt conveyor mechanisms are respectively suspended at the two ends of the bottom plate of the box beam and extend in a horizontal direction. The extending direction is perpendicular to the length direction of the box beam, and the belt of the belt conveyor mechanism is flush with the bottom of the mounting frame.

[0008] The horizontal section of the second connecting arm is strip-shaped, and the top and bottom surfaces are both provided with two strip grooves extending along the length direction. There are two pairs of support wheels in the same row, which are respectively arranged at both ends of the mounting frame and rollingly fit in the corresponding strip grooves.

[0009] The driving wheel of the belt conveying mechanism is driven to rotate by a stepping motor, and the first motor is a servo motor.

[0010] The horizontal section of the third connecting arm is an electric telescopic rod.

[0011] A second technical solution for achieving the purpose of the present invention is: a method for repairing a box beam bottom plate using any of the above-mentioned repair robots comprises the following steps:

[0012] 1) In an initial state, the robot body is supported on the belt conveyor mechanism at the first end through the mounting frame, and the mounting frame is close to the second vertical section of the second connecting arm;

[0013] 2) The first electromagnet is energized and adsorbed on the bottom of the box beam, the second electromagnet is de-energized, the first motor is energized, and the support wheel is driven to rotate, so that the second connecting arm moves toward the belt conveying mechanism at the second end to the first vertical section of the mounting frame close to the second connecting arm;

[0014] 3) The second electromagnet is powered on and adsorbed on the bottom of the box beam, the first electromagnet is powered off, the first motor is powered on, and the support wheel is driven to rotate, so that the installation frame moves toward the belt conveyor at the second end until the installation frame is close to the second vertical section of the second connecting arm;

[0015] 4) Repeat steps 2) and 3) to support the robot body on the belt conveyor mechanism at the second end through the mounting frame, and the mounting frame is close to the first vertical section of the second connecting arm;

[0016] 5) The belt conveyor mechanism at the second end drives the robot body to move vertically along the length direction of the box beam;

[0017] 6) The first electromagnet is energized and adsorbed on the bottom of the box beam, the second electromagnet is de-energized, the first motor is energized, and the support wheel is driven to rotate, so that the second connecting arm moves toward the belt conveying mechanism at the first end to the second vertical section of the mounting frame close to the second connecting arm;

[0018] 7) The second electromagnet is energized and adsorbed on the bottom of the box beam, the first electromagnet is de-energized, the first motor is energized, and the support wheel is driven to rotate, so that the installation frame moves toward the belt conveyor mechanism at the first end, until the installation frame is close to the first vertical section of the second connecting arm;

[0019] 8) Repeat steps 6) and 7) to make the robot body in the initial position and change the vertical position;

[0020] 9) The belt conveyor mechanism at the first end drives the robot body to move vertically along the length direction of the box girder. The robot body reciprocates between the belt conveyor mechanism at the first end and the belt conveyor mechanism at the second end. During the translation of the robot body, the third connecting arm rotates, and the camera captures the area where the bottom of the box girder passes, and synthesizes the image of the bottom of the box girder through an image algorithm for manual inspection to complete the maintenance work.

[0021] Specifically, the image algorithm in step 9) includes the following steps:

[0022] 1) The width of the annular area scanned by the camera when it rotates one circle is s. After the camera rotates one circle, the length of the horizontal section of the third connecting rod extends outward by s. After scanning n times, the width of the scanned annular area is recorded as S=n*s;

[0023] 2) During the robot's alternating movement, the single movement distance is k, the robot moves m times alternately, and the translation distance is recorded as K = m*k;

[0024] 3) Establishing a coordinate system based on the annular area width S and the translation distance K;

[0025] 4) intercepting a valid area within a fixed coordinate from the annular area with a width of S obtained in step 1);

[0026] 5) The overlapping areas of the intercepted valid areas along the K coordinate are faded;

[0027] 6) Overlay the images to form a rectangular image for manual inspection.

[0028] 8. The method according to claim 7, characterized in that the effective area in step 4) is a right-angled trapezoid or an isosceles trapezoid with an arc side as the hypotenuse.

[0029] The above technical solution has the following beneficial effects:

[0030] 1. The box girder bottom plate maintenance robot includes two storage areas and a robot body, and a power supply is provided in the robot body. The robot body includes a mounting frame, a first connecting arm, a second connecting arm, and a third connecting arm, wherein the mounting frame is used to install each connecting arm. Two rows of support wheels are provided in the mounting frame, and the number of support wheels in the same row is at least two and they are located at the same height, and at least one support wheel is driven to rotate by a first motor. The first connecting arm is fixed to the top of the mounting frame and extends vertically upward. A coil is wound on the first connecting arm and is electrically connected to the power supply to form a first electromagnet. When the first electromagnet is energized, it can be adsorbed on the box girder bottom plate, so that the mounting frame is suspended below the box girder bottom plate. The second connecting arm is in a U-shaped structure, the horizontal section of the second connecting arm is clamped between two rows of support wheels, the two vertical sections of the second connecting arm extend out of the mounting frame, and the height is the same as that of the first connecting arm, the two vertical sections of the second connecting arm are respectively wound with coils and electrically connected to the power supply to form a second electromagnet, the second connecting arm cooperates with the mounting bracket through the support wheels and the horizontal section, so that the second connecting arm and the mounting bracket can move relatively in the horizontal direction and are stable, when the second electromagnet is energized, it can be adsorbed on the bottom plate of the box beam, so that the mounting frame is suspended below the bottom plate of the box beam. The third connecting arm is in an L-shaped structure, the vertical section of the third connecting arm is arranged at the bottom of the mounting frame, and is driven to rotate by the second motor, the extension end of the horizontal section of the third connecting arm exceeds the projection range of the mounting frame, and a camera is provided, the camera is driven to translate by the mounting frame, and during the translation process, it rotates along the translation trajectory to achieve a larger camera coverage range. The storage area includes a belt conveyor mechanism, and the two belt conveyor mechanisms are respectively suspended at both ends of the bottom plate of the box beam, extending in the horizontal direction, and the extending direction is perpendicular to the length direction of the box beam. The belt of the belt conveyor mechanism is flush with the bottom of the mounting frame. The robot body is supported on the belt conveyor mechanism through the mounting frame, and the position of the second connecting arm is controlled so that the center of gravity of the robot body is located on the belt conveyor mechanism, thereby ensuring the stability of the robot body on the belt conveyor mechanism. The robot body is used for charging and maintenance, which can effectively reduce the intensity of manual labor and ensure manual safety.

[0031] 2. The horizontal section of the second connecting arm is strip-shaped, and the top and bottom surfaces are provided with two strip grooves extending along the length direction. There are two pairs of support wheels in the same row, which are respectively arranged at both ends of the mounting frame and rollingly fitted in the corresponding strip grooves to ensure the relative stability between the second connecting arm and the mounting frame, as well as the mutual support strength.

[0032] 3. The inspection method of the present invention utilizes the camera to make circular movements during translation, and obtains a larger area of ​​annular images by extending the horizontal section of the third connecting arm outward, thereby improving the scanning efficiency of the inspection robot and reducing the number of reciprocating movements of the robot. By cutting the effective area from the circular scanning image and splicing it to form a rectangular image, the problem of inaccurate damage positioning caused by lateral tensile deformation in a single image can be avoided, and the blind area of ​​the weld of the stiffening rib can be eliminated, and the inspection image of the stiffening rib of the bottom plate of the box girder can be accurately obtained.

[0033] Further description is given below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of the present invention;

[0035] Figure 2 This is a schematic diagram of the robot body of the present invention staying in the storage area;

[0036] Figure 3 The view of step 1) in the image algorithm of the present invention;

[0037] Figure 4 The view of step 2) in the image algorithm of the present invention;

[0038] Figure 5 The view of step 3) in the image algorithm of the present invention;

[0039] Figure 6 The view of step 4) in the image algorithm of the present invention;

[0040] Figure 7 It is the view of step 5) in the image algorithm of the present invention;

[0041] Figure 8 This is the view of step 6) in the image algorithm of the present invention.

[0042] In the accompanying drawings, 1 is a storage area, 2 is a robot body, 3 is a mounting frame, 4 is a first connecting arm, 5 is a second connecting arm, 6 is a third connecting arm, 7 is a supporting wheel, 8 is a first motor, 9 is a first electromagnet, 10 is a second electromagnet, 11 is a second motor, 12 is a camera, and 13 is a belt conveyor mechanism. DETAILED DESCRIPTION

[0043] Example 1

[0044] See also Figure 1 and Figure 2 The box girder bottom plate maintenance robot includes two storage areas 1 and a robot body 2. A power supply is provided in the robot body 2, and the power supply is usually a rechargeable lithium battery. The robot body 2 includes a mounting frame 3, a first connecting arm 4, a second connecting arm 5, and a third connecting arm 6. Usually, the mounting frame 3 is set as a cubic frame. Two rows of support wheels 7 are provided in the mounting frame 3. The number of support wheels 7 in the same row is at least two and they are located at the same height. At least one support wheel is driven to rotate by a first motor 8. In this embodiment, the number of support wheels 7 in the same row is two pairs, which are respectively arranged at both ends of the mounting frame 3. The first motor 8 is a servo motor. The first connecting arm 4 is fixed to the top of the mounting frame 3 and extends vertically upward. A coil is wound around the first connecting arm and is electrically connected to the power supply to form a first electromagnet 9. The second connecting arm 5 is in a U-shaped structure, the horizontal section of the second connecting arm 5 is clamped between two rows of support wheels 7, the two vertical sections of the second connecting arm 5 extend out of the mounting frame 3, and the height is the same as that of the first connecting arm 4, the two vertical sections of the second connecting arm are respectively wound with coils and electrically connected to the power supply to form a second electromagnet 10, in this embodiment, the horizontal section of the second connecting arm 4 is in a strip shape, and the top and bottom surfaces are both provided with two strip grooves extending along the length direction, and rolling fit in the corresponding strip grooves. The third connecting arm 6 is in an L-shaped structure, the vertical section of the third connecting arm 6 is provided at the bottom of the mounting frame 3, and is driven to rotate by the second motor 11, the extended end of the horizontal section of the third connecting arm 6 exceeds the projection range of the mounting frame 3, and is provided with a camera 12, in this embodiment, the horizontal section of the third connecting arm 6 is an electric telescopic rod, so that the camera can be translated outward. The storage area 1 includes a belt conveyor mechanism 13, a driving wheel of the belt conveyor mechanism 13 is driven to rotate by a stepper motor, and the two belt conveyor mechanisms 13 are respectively suspended at both ends of the bottom plate of the box beam, extending in the horizontal direction, and the extension direction is perpendicular to the length direction of the box beam, and the belt of the belt conveyor mechanism 13 is flush with the bottom of the mounting frame.

[0045] In order to ensure safety, a safety rope is also included, the two ends of which are respectively fixedly connected to the two ends of the box beam, and a safety support arm is arranged on the installation frame, and the extended end of the safety support arm is sleeved on the safety rope.

[0046] Example 2

[0047] The method for repairing the bottom plate of a box beam using the repair robot of Example 1 comprises the following steps:

[0048] 1) In an initial state, the robot body is supported on the belt conveyor mechanism at the first end through the mounting frame, and the mounting frame is close to the second vertical section of the second connecting arm;

[0049] 2) The first electromagnet is energized and adsorbed on the bottom of the box beam, the second electromagnet is de-energized, the first motor is energized, and the support wheel is driven to rotate, so that the second connecting arm moves toward the belt conveying mechanism at the second end to the first vertical section of the mounting frame close to the second connecting arm;

[0050] 3) The second electromagnet is powered on and adsorbed on the bottom of the box beam, the first electromagnet is powered off, the first motor is powered on, and the support wheel is driven to rotate, so that the installation frame moves toward the belt conveyor at the second end until the installation frame is close to the second vertical section of the second connecting arm;

[0051] 4) Repeat steps 2) and 3) to support the robot body on the belt conveyor mechanism at the second end through the mounting frame, and the mounting frame is close to the first vertical section of the second connecting arm;

[0052] 5) The belt conveyor mechanism at the second end drives the robot body to move vertically along the length direction of the box beam;

[0053] 6) The first electromagnet is energized and adsorbed on the bottom of the box beam, the second electromagnet is de-energized, the first motor is energized, and the support wheel is driven to rotate, so that the second connecting arm moves toward the belt conveying mechanism at the first end to the second vertical section of the mounting frame close to the second connecting arm;

[0054] 7) The second electromagnet is energized and adsorbed on the bottom of the box beam, the first electromagnet is de-energized, the first motor is energized, and the support wheel is driven to rotate, so that the installation frame moves toward the belt conveyor mechanism at the first end, until the installation frame is close to the first vertical section of the second connecting arm;

[0055] 8) Repeat steps 6) and 7) to make the robot body in the initial position and change the vertical position;

[0056] 9) The belt conveyor mechanism at the first end drives the robot body to move vertically along the length direction of the box beam. The robot body reciprocates between the belt conveyor mechanism at the first end and the belt conveyor mechanism at the second end. During the translation of the robot body, the third connecting arm rotates, and the camera captures the area where the bottom of the box beam passes, and synthesizes the bottom image of the box beam for manual inspection through the image algorithm to complete the maintenance work. The image algorithm includes the following steps:

[0057] 1) The width of the annular area scanned by the camera after one rotation is s. After the camera rotates one rotation, the length of the horizontal section of the third connecting rod extends outward by s. After n scanning times, the width of the scanned annular area is recorded as S = n*s. Figure 3 ;

[0058] 2) During the robot's alternating movement, the single moving distance is k, the robot moves m times, and the translation distance is recorded as K = m*k. Figure 4 ;

[0059] 3) Establish a coordinate system based on the annular area width S and the translation distance K, see Figure 5 ;

[0060] 4) The effective area within the fixed coordinates is intercepted from the annular area with a width of S obtained in step 1). Specifically, the effective area is a right-angled trapezoid or an isosceles trapezoid with an arc side as the hypotenuse. Figure 6 ;

[0061] 5) The overlapping areas of the intercepted valid areas along the K coordinate are faded, see Figure 7 ;

[0062] 6) Overlay the images to form a rectangular image for manual inspection, see Figure 8 .

[0063] There is a large-span steel box girder in a certain area with a span of 50m. Its main function is to drive vehicles. The connected area is an urban road separated by the Third Ring Road. It crosses the Third Ring Road Expressway. The width of each bridge bottom plate is 10m and the upper width is 15m.

[0064] According to conventional methods, the road needs to be shut down for the maintenance of steel box girders, which causes the following problems: high risk and long cycle. Maintenance is required every two years. During maintenance, manual lifting vehicles are required to lift to the bottom of the steel box girder and rely on manual visual judgment. Manual inspection requires the six lanes of the Third Ring Road Expressway to be shut down separately. Each lane starts from the preparation work (that is, in addition to obtaining approval from the Transportation Commission at the beginning, a long-distance diversion warning device must be set up first, such as a warning sign for construction ahead, and then a personnel lifting vehicle needs to be driven under the steel box girder, and then the lifting operation is carried out under the supervision of the on-site supervisor. Therefore, each shift requires workers, drivers, on-site supervisors, etc., and no less than 3 to 5 people). It takes 2.5 days to shut down the road, and a total of no less than 15 days of maintenance time, which has a great impact on vehicle speed and traffic flow.

[0065] Robot inspections are routine and do not have the above problems. For some existing municipal bridges, for safety reasons, height limit warnings need to be set during inspections to avoid the risk of collisions between large vehicles and robots.

Claims

1. A box girder bottom plate maintenance robot, characterized in that: The robot comprises two storage areas (1) and a robot body (2). The robot body (2) is provided with a power source. The robot body (2) comprises a mounting frame (3), a first connecting arm (4), a second connecting arm (5), and a third connecting arm (6). The mounting frame (3) is provided with two rows of support wheels (7), the number of support wheels (7) in the same row is at least two and they are located at the same height, at least one support wheel is driven to rotate by a first motor (8), The first connecting arm (4) is fixed to the top of the mounting frame (3) and extends vertically upward. A coil is wound around the first connecting arm and is electrically connected to a power source to form a first electromagnet (9). The second connecting arm (5) is in a U-shaped structure. The horizontal section of the second connecting arm (5) is clamped between two rows of supporting wheels (7). The two vertical sections of the second connecting arm (5) extend out of the mounting frame (3) and have the same height as the first connecting arm (4). Coils are respectively wound around the two vertical sections of the second connecting arm and are electrically connected to a power source to form a second electromagnet (10). The third connecting arm (6) is in an L-shaped structure. The vertical section of the third connecting arm (6) is arranged at the bottom of the mounting frame (3) and is driven to rotate by a second motor (11). The extended end of the horizontal section of the third connecting arm (6) exceeds the projection range of the mounting frame (3) and is provided with a camera (12). The storage area (1) comprises a belt conveyor mechanism (13), wherein two belt conveyor mechanisms (13) are respectively suspended at two ends of the bottom plate of the box beam, extending in a horizontal direction, and the extending direction is perpendicular to the length direction of the box beam, and the belts of the belt conveyor mechanisms (13) are flush with the bottom of the mounting frame.

2. The box beam bottom plate maintenance robot according to claim 1, characterized in that: The horizontal section of the second connecting arm (4) is in the shape of a strip, and the top and bottom surfaces are both provided with two strip grooves extending in the length direction. The number of supporting wheels (7) in the same row is two pairs, which are respectively arranged at the two ends of the mounting frame (3) and rollingly fit in the corresponding strip grooves.

3. The box beam bottom plate maintenance robot according to claim 1, characterized in that: The driving wheel of the belt conveying mechanism (13) is driven to rotate by a stepping motor, and the first motor (8) is a servo motor.

4. The box beam bottom plate maintenance robot according to claim 1, characterized in that: The horizontal section of the third connecting arm (6) is an electric telescopic rod.

5. A method for repairing a box beam bottom plate using a repair robot according to any one of claims 1 to 4, characterized in that: The steps include: 1) In an initial state, the robot body is supported on the belt conveyor mechanism at the first end through the mounting frame, and the mounting frame is close to the second vertical section of the second connecting arm; 2) The first electromagnet is energized and adsorbed on the bottom of the box beam, the second electromagnet is de-energized, the first motor is energized, and the support wheel is driven to rotate, so that the second connecting arm moves toward the belt conveying mechanism at the second end to the first vertical section of the mounting frame close to the second connecting arm; 3) The second electromagnet is powered on and adsorbed on the bottom of the box beam, the first electromagnet is powered off, the first motor is powered on, and the support wheel is driven to rotate, so that the installation frame moves toward the belt conveyor at the second end until the installation frame is close to the second vertical section of the second connecting arm; 4) Repeat steps 2) and 3) to support the robot body on the belt conveyor mechanism at the second end through the mounting frame, and the mounting frame is close to the first vertical section of the second connecting arm; 5) The belt conveyor mechanism at the second end drives the robot body to move vertically along the length direction of the box beam; 6) The first electromagnet is energized and adsorbed on the bottom of the box beam, the second electromagnet is de-energized, the first motor is energized, and the support wheel is driven to rotate, so that the second connecting arm moves toward the belt conveying mechanism at the first end to the second vertical section of the mounting frame close to the second connecting arm; 7) The second electromagnet is energized and adsorbed on the bottom of the box beam, the first electromagnet is de-energized, the first motor is energized, and the support wheel is driven to rotate, so that the installation frame moves toward the belt conveyor mechanism at the first end, until the installation frame is close to the first vertical section of the second connecting arm; 8) Repeat steps 6) and 7) to make the robot body in the initial position and change the vertical position; 9) The belt conveyor mechanism at the first end drives the robot body to move vertically along the length direction of the box girder. The robot body reciprocates between the belt conveyor mechanism at the first end and the belt conveyor mechanism at the second end. During the translation of the robot body, the third connecting arm rotates, and the camera captures the area where the bottom of the box girder passes, and synthesizes the image of the bottom of the box girder through an image algorithm for manual inspection to complete the maintenance work.

6. The method according to claim 5, characterized in that Step 9) The image algorithm comprises the following steps: 1) The width of the annular area scanned by the camera when it rotates one circle is s. After the camera rotates one circle, the length of the horizontal section of the third connecting rod extends outward by s. After scanning n times, the width of the scanned annular area is recorded as S=n*s; 2) During the robot's alternating movement, the single movement distance is k, the robot moves m times alternately, and the translation distance is recorded as K = m*k; 3) Establishing a coordinate system based on the annular area width S and the translation distance K; 4) intercepting a valid area within a fixed coordinate from the annular area with a width of S obtained in step 1); 5) The overlapping areas of the intercepted valid areas along the K coordinate are faded; 6) Overlay the images to form a rectangular image for manual inspection.

7. The method according to claim 5, characterized in that Step 4) The effective area is a right-angled trapezoid or an isosceles trapezoid with an arc side as the hypotenuse.

Images