The Design and Performance Testing of A MEMS Safety and Arming Device with an Insurance Lock

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(Science and Technology on Applied Physical Chemistry Laboratory，Shaanxi Applied Physics and Chemistry Research institute，Xi’an Shaanxi 710061，China)

Abstract:The Safety and Arming Device is the core component of the safety system which acts as the explosion and deinsurance function in the fuze safety system.The MEMSSafety and Arming device with an insurance lock was designed.The device used the recoil force and centrifugal force to relieve the insurance.Results show that when the recoil force greater than 26 000 g n，centrifugal rotational speed greater than 18 000 rpm the device can successfully realize safe and arming functions.

Key words:MEMS；setback arming；safety and arming device

MEMSsecurity mechanism is proposed with the development of high-tech weapons.The insurance mechanism using MEMStechnology adopts a flat structure design，which has the characteristics of small size，light weight and low cost.It has become an important way to solve the miniaturization of security systems.At present，many domestic institutions and universities have related research on MEMS security institutions.The honor of Nanjing University of Science and Technology，Liu Xuan，Tong Xu，Li Laifu，etc.designed the back-seat insurance of the Fuse Credit[1－4]；Yang Hongliang and others performed the simulation design of the MEMSsecurity mechanism[5]；Li Wendi，Zheng Can，etc.Have also studied the deferred insurance mechanism[6－7]；Shenyang Ligong Shi Chunjing and others have designed and analyzed the MEMS security mechanism[8]；Fan Chenyang，Tian Zhongwang and others have studied the slider locking mechanism[9－10]；Liu Jiakai，Li Dongjie，etc.researched the way of unlocking the security mechanism[11－12].This paper designs a MEMSsecurity mechanism with safety lock and conducts performance tests on it.The security device can effectively complete the function of releasing the insurance，can provide basic technology for the design and manufacture of MEMSsecurity mechanism，and provide support technology for the transformation of existing weapons and equipment.

1 Structural design and simulation of safety and arming device

The schematic diagram of the design principle of safety and arming device with a safety lock was showed in Figure 1.Its components included the rear seat slider，safety lock，centrifugal slider，all components were limited to the frame on the base plate.Its working principle was when the recoil slider moves downward in the opposite direction of the spring tension，and the deformation of the safety lock rod releases the constraint on the centrifugal slider.The centrifugal slider moves to the right under the action of rotational acceleration and under the action of continuous rotational acceleration The centrifugal slider moves to the right and is locked，and the explosive transfer strip connects the initiating charge and the explosive transfer charge to form an explosion transfer sequence，which is in the unlocked position.If the command slider moves prematurely，or does not rotate，or the recoil is insufficient，the system will be in a safe state or make the safety invalid.

Fig.1 Picture of Schematic diagram of MEMSsecurity mechanism with safety lock

1.1 Design of the slider

1.1.1 Structural design of micro-spring

The micr-spring is an important energy storage element in the fuze，which can realize the transmission of energy and force.It is an important part to ensure the safety of the fuze safety system and the reliable function after launch.It not only provides the elastic force required by the system，but also transmits energy.Planar micro-spring structures that can be used in MEMSsecurity mechanisms include“L”，“S”，“Z”，and“B”types.Since there have been many literature studies on the stiffness of various microsprings，this paper chooses the“S”type micro-spring with moderate stiffness and smooth transition.

1.1.2 Design and simulation of slider

The slider is composed with a chuck and a spring.The working principle of the chuck is that when the external environmental force is received，the slider moves at a certain speed.The chuck on the slider interacts with the holder on the substrate after contact.First，the chuck deforms and moves into the holder.After the chuck fully enters the chock，it returns to its original state under the rigidity of its own beam.At this time，it is locked in the process of the slider entering the chock.

The simulation of the slider chuck is shown in Figure 2.It can be seen that the bending part of the two fins spread out by the slider chuck is subjected to the greatest stress，which is the dangerous cross section.When the stress at the dangerous section of the structure exceeds the yield limit of the material，plastic deformation will occur first at the dangerous section of the structure.The slider chuck cannot rebound and cannot be stuck.

Fig.2 Picture of the simulation diagram of limiter

For the plastic deformation of the chuck.Improve the chuck to the structure shown in Figure 3(b)，increase the opening angle of the two wings at the tail of the chuck，and increase the length of the fins so that they will not plastically deform when they are caught in the holder.

1.2 The design of the limit

The limit of the centrifugal slider in this subject is the cantilever beam.Its working principle is that when the recoil slider is in a safe state，the centrifugal slider is stuck at the initial assembly position shown in the figure by the protrusion on the cantilever beam，and cannot move.When the projectile is launched，the recoil slider Sinks under the action of recoil force，contacts with the cantilever beam and then deforms it.When the recoil force is sufficient and the action time is long enough，the recoil slider moves to the bottom of the base plate and is locked at the bottom of the base plate；When the cantilever beam is deformed，the protrusion is pulled out of the groove of the centrifugal slider to release the first insurance of the flameproof plate.When the follow-up insurance is completely released，the centrifugal slider moves to the right under the action of centrifugal force.

Fig.3 Picture of the limiter shape

Fig.4 Picture of cantilever

2 Performance test of micro-explosionproof and flame-proof devices

The physical diagram of the improved microsecurity mechanism is shown in Figure 5.The structural parameters are spring width 0.1 mm，section number 8，chuck spring width 0.2 mm，and bending radius R10.

Fig.5 Picture of the improved micro-security organization

2.1 Performance test of the rear seat slider:

The rear seat slider experiment mainly uses a Marshall hammer to apply an impact load at different g values to the rear seat slider that has been assembled into the frame.After the hammering is completed，observe whether the rear seat slider assembled in the frame is in the impact Movement in place，deformation of the rear seat spring.Since this test only checks the movement of the rear seat slider，a simple frame with only the rear seat slide rail is used in the test.The physical picture of the structure is shown in Figure 6.

Fig.6 Picture of the thematic diagram of the rear seat slider structure

The experimental results are shown in Table 1.The experimental results show that when the recoil force is less than 23 000gn(17 teeth)，the slider cannot fully enter the slot.When the recoil force reaches 26 000gn(18 teeth)，the rear seat slider After entering the card，the card is stuck and the rear seat insurance is released.

Table 1 Rear seat insurance function test results

2.2 Performance test of the limit mechanism

The cantilever beam designed in this subject is shown in Fig.7，and verified by the Marshall hammer test，the rear seat slider can move into place when the rear seat is overloaded at 26 000gn(at 18 teeth)，and the cantilever beam limit mechanism can release the centrifugal slider Constraints.

Fig.7 Picture of the Deformation of the limit beam under different recoil forces

2.3 Performance test of centrifugal slider

The centrifugal safety mechanism is a mechanical insurance mechanism that uses the centrifugal force generated by the high-speed rotation of the projectile to release the insurance.The mechanism is deformed downward，and the limit boss releases the constraint on the centrifugal slider，and the centrifugal slider moves to the right under the action of centrifugal force.

In this paper，the centrifugal slider is installed in the card slot and installed in the special fixture of the centrifuge.Table 2 shows the motion performance of the micro mechanism under different speeds.

Table 2 Sample of a centrifugal silder

The table 2 shows that the centrifugal slider can move into place when the rotation speed is 18 000 rpm and the action time is 1 s.

3 Conclusion

①A micro-security mechanism with a safety lock is designed，which is prepared by a combination of MEMS technology and precision mechanical processing methods.The design uses recoil and centrifugal force to release the security.

②The manufactured micro-security mechanism with a safety lock can normally release the security function when the recoil force is greater than 26 000gnand the centrifugal rotation speed is greater than 18 000 rpm.