Please select the most similar patent number from A, B, C and D. Which number is?
A double-layer dumb drum that has a sanding belt adjustment function, comprising an upper-layer elastic body, a striking edge strip, an upper base plate, a sanding belt adjusting device, an inner resonance cavity, an outer resonance cavity, a lower-layer elastic body, and a lower base plate. The upper-layer elastic body is fixed above the upper base plate, the inner resonance cavity and the outer resonance cavity are disposed below the upper base plate, the sanding belt adjusting device is disposed in the inner resonance cavity, and a lower part of the inner resonance cavity is sealed by means of the outer resonance cavity; the lower-layer elastic body is fixedly connected above the lower base plate, several contact points are disposed below the outer resonance cavity, and the outer resonance cavity abuts with an upper part of the lower-layer elastic body by means of the contact points; and the upper base plate and the lower base plate are connected and fixed one to the other by means of several connection screws. In using the double-layer dumb drum, the feel and hitting speed may not only be practiced, but the sanding belt may also be adjusted and the sound of an actual snare drum may be simulated, so that beginners may experience the sound effect of a real snare drum when practicing on the dumb drum, thus feeling the sound effect of a real snare drum in advance and speeding up the learning process.
A: A robot protection device having an anti-collision function, comprising a protection device body (1). A bottom plate (2) is connected below the protection device body (1); a retractable arm (15) is mounted on the lower bottom surface of the bottom plate (2); the tail end of the retractable arm (15) is provided with a sensor (16); a support palm (17) is fixed below the sensor (16); a clamping seat (3) is provided above the bottom plate (2); a base (4) is embedded in a surface of the clamping seat (3); an elastic column (8) is connected above the base (4); a connecting rod (7) is fixed on a surface of the elastic column (8); a force bearing plate (5) is welded on the other end of the connecting rod (7); a surface of the force bearing plate (5) is provided with a silicone pad (6); a movable plate (9) is mounted on the right side of the elastic column (8); two ends of the movable plate (9) are connected to rolling shafts (14). The robot protection device having an anti-collision function is provided with an anti-falling means, falling of a robot can be sensed in advance, and the robot can be supported to be prevented from being damaged due to falling to the ground.
B: A cajon has a frame (1) formed by four edgings, namely, an upper edging (11), a lower edging (12), a left edging (13), and a right edging (14). A striking surface (10) is fixedly disposed on the frame (1). Front ends of a left side plate (4) and a right side plate (5) are separately hinged on the left edging (13) and the right edging (14) of the frame (1). Front ends of an upper side plate (2) and a lower side plate (3) are separately connected to the upper edging (11) and the lower edging (12). Guide posts (22, 32, 42, 52) disposed on rear ends of the upper side plate (2), the lower side plate (3), the left side plate (4), and the right side plate (5) are separately inserted into guide holes (220, 320, 420, 520) disposed on corresponding positions on a rear plate (6). Screw guide blocks (7) are separately disposed on surfaces facing the inside of a box, of the upper side plate (2) and the lower side plate (3). Screw guide holes (70) are arranged on the screw guide blocks (7). Screws (8) pass through rear board screw guide holes (600) and the screw guide holes (70) arranged on the screw guide blocks (7) are connected inside nut guide holes (111, 121) in a screw manner, so that the screws (8) connect the rear plate (6), the upper side plate (2) and the frame (1), and the screws (8) connect the rear plate (6), the lower side plate (3) and the frame (1). A military drum type snare facing the striking surface (10) is hinged on the lower edging (12). Disassembly, assembly, transportation and carry of the cajon are more convenient, and sound effect and tone quality are various.
C: An anti-collision robot, comprising a protection device body (1). A bottom plate (2) is connected below the protection device body (1); a retractable arm (15) is mounted on the lower bottom surface of the bottom plate (2); the tail end of the retractable arm (15) is provided with a sensor (16); a support palm (17) is fixed below the sensor (16); a clamping seat (3) is provided above the bottom plate (2); a base (4) is embedded in a surface of the clamping seat (3); an elastic column (8) is connected above the base (4); a connecting rod (7) is fixed on a surface of the elastic column (8); a force bearing plate (5) is welded on the other end of the connecting rod (7); a surface of the force bearing plate (5) is provided with a silicone pad (6); a movable plate (9) is mounted on the right side of the elastic column (8); two ends of the movable plate (9) are connected to rolling shafts (14). The anti-collision robot is provided with an anti-falling device, falling of the robot can be sensed in advance, and the robot can be supported to be prevented from being damaged due to falling to the ground.
D: A flat disc six-dimensional force sensor based on an eddy current effect, a detection method, and a smart device, the force sensor comprising: an outer shell (1), an elastic body (2), a first probe (3), a second probe (4), a third probe (5), and a fourth probe (6), the elastic body (2) being arranged inside the outer shell (1), the elastic body (2) comprising a bottom plate, a detection plate (202), and a first boss (201), support columns (209) being arranged between the bottom plate and the detection plate (202), the detection plate (202) being positioned above the bottom plate, the first boss (201) being arranged above the detection plate (202), a sink (206) being arranged on the lower surface of the detection plate (202), the first probe (3), the second probe (4), the third probe (5), and the fourth probe (6) respectively being uniformly distributed on the bottom plate and not being in contact with the detection plate (202), and the first probe (3), the second probe (4), the third probe (5), and the fourth probe (6) being capable of sensing the amount of deformation and the direction of deformation of the elastic body (2) by means of the current exciting eddy current magnetic field changes. The present force sensor has the characteristics of having a small volume and strong bearing capacity and being interference-resistant, and the force measurement range and accuracy of the sensor can be adjusted directly from the machine body, being highly flexible.
Answer: B