As a graduate researcher specializing in vehicle engineering, I have dedicated my thesis work to developing a comprehensive impact explosion protection system tailored for electric vehicle (EV) battery pack dynamic crash testing. The project is driven by a pressing need in the automotive safety domain: after a high-energy dynamic impact, the EV battery pack can rapidly undergo thermal runaway, leading to smoke, fire, or even violent explosion. Standard indoor testing facilities often lack a dedicated system that both performs the impact and safely handles the post-impact hazards. In this paper, I present the full design process, covering system architecture, mechanical structure calculations, hardware selection, software development, and experimental validation. The proposed system has been deployed and verified in a commercial new energy vehicle testing center, significantly improving operator safety and test reliability.
1. Introduction and Motivation
The rapid adoption of electric vehicles has placed unprecedented emphasis on the safety of the EV battery pack. Unlike conventional fuel tanks, the battery pack stores a huge amount of electrochemical energy. When subjected to severe mechanical abuse such as side collisions, bottom impacts, or dynamic intrusions, the internal cells may deform, short-circuit, and generate intense heat. Data from fire departments indicate that a substantial proportion of EV fire accidents are initiated by mechanical damage to the battery pack. Therefore, standard test procedures, such as those described in C-NCAP, require dynamic impact tests on the complete EV battery pack. However, conducting such tests inside a laboratory is inherently dangerous. The moment after impact, the pack may start to smoke or burn within seconds to minutes, posing an immediate threat to test personnel and facility integrity.
My literature review reveals that most existing studies focus on cell-level or module-level abuse tests, using custom-made indentation devices or drop towers. While these studies provide useful material data, they do not address the engineering challenge of handling a full-size EV battery pack after a realistic dynamic trolley impact. Moreover, typical post-test procedures involve manual forklift operations to immerse the damaged pack into a water tank, which is hazardous and slow. No published work describes an integrated system that can rigidly hold a full EV battery pack, allow a guided dynamic impact, and then automatically (or semi-automatically) submerge the pack into a flameproof pool within a critical time window. This gap motivated my research.
My goal was to design and implement an impact explosion protection system for EV battery pack dynamic testing, satisfying the following requirements:
- To hold the EV battery pack firmly during high-energy trolley impact, preventing secondary collisions.
- To provide guided vertical motion so that after impact, the pack can be lowered into a water-filled pit for cooling and explosion suppression.
- To have both automatic and manual release mechanisms, including a quick emergency release feature.
- To ensure high reliability, remote operation, and real-time status monitoring.
The rest of the article is organized according to my design methodology: total system architecture, mechanical design and calculations, motion control planning, hardware selection, software implementation, and finally, field testing results.
2. System Architecture and Design Requirements
2.1 System Functional Analysis
The system is placed in a frontal crash test laboratory where a fixed reinforced-concrete barrier is available. The barrier is at least 3 m wide and 1.5 m high, with a mass above 70 tons. In our test configuration, the EV battery pack is mounted on a movable steel platform (the “table”) that, in its locked position, is closely pressed against a vertical backstop that is attached to the concrete barrier. A guided trolley with an impact head (either cylindrical D=254 mm or spherical D=150 mm) strikes the EV battery pack at a specified speed, typically 20 km/h, with trolley mass up to 1500 kg or more.
C-NCAP requirements for vehicle impact tests demand a flat, smooth runway and a rigid barrier. My system must coexist with those constraints. From the functional perspective, the system has to:
- Support the EV battery pack and its mounting fixture with a maximum total mass of 800 kg (or in later verification, larger packs with additional mass).
- Lock the platform with a sufficient force during impact.
- Provide horizontal and pitch-direction guiding so that the platform does not translate or tilt when moving vertically.
- Lower the platform into a fire-protection water pool at a controlled speed.
- Possess safety interlocks to prevent unintended motion.
2.2 Determination of Power Sources
For the vertical lifting and lowering, I selected an electric wire-rope hoist driven by a three-phase asynchronous motor. A frequency converter controls the motor speed, enabling smooth acceleration and deceleration. For the locking/unlocking of the platform to the backstop, I selected a pneumatic system using cylinders because of its simplicity, low cost, fast response, and inherent safety. The lock/unlock mechanism is a wedge-type combined with a crank-linkage mechanism. Pneumatic cylinders push the linkage, which drives a sliding wedge block to press against a fixed wedge block mounted on the platform. This design produces a strong locking force with a relatively small cylinder force due to the wedge amplification effect.
For the control system, I chose a distributed architecture based on a Siemens S7-1200 PLC (CPU 1215C) with ET200SP remote I/O modules. The human-machine interface (HMI) is a 10.1-inch resistive touchscreen. The communication is via industrial Ethernet (Profinet). A remote control with buttons enables local operation near the equipment, while a control room has an emergency release.
2.3 Modular Control Approach
To make the program easier to debug and maintain, I divided the control software into four function modules: (1) lock control, (2) unlock control, (3) lift/lowering control, and (4) sensor-signal checking. Each module is written as a separate FC (function) in TIA Portal V18 and called by the main OB1 program. The modular structure minimizes interference among components and improves system reliability.
3. Design of Mechanical Structures
All 3D models were built using SolidWorks. The primary structures include the platform (table), locking/unlocking mechanism, horizontal guide assembly, pitch guide assembly, wire-rope pulley supports, safety pins, and manual release levers.
3.1 Platform Structure
The platform is a welded steel frame with a top plate. The top plate contains multiple circular holes and threaded holes. The circular holes serve as flow passages when the platform enters and exits the water pit, reducing water resistance and pressure differences. The threaded holes allow flexible mounting of the EV battery pack fixture. The platform has two H-beam guides on its rear side, which are used as guide channels for the pitch-direction guide rails.
A three-dimensional representation of the platform is shown below:
The platform is made of Q235 structural steel. The total mass of the movable platform itself is 2000 kg. In the initial design calculations, the maximum EV battery pack and fixture mass was assumed to be 800 kg. Later, during field trials, the system was tested with even heavier packs by adjusting the frequency converter parameters to lower the descent speed and avoid overvoltage trips.
3.2 Locking Mechanism
Four locking mechanisms are arranged symmetrically on the left and right sides of the backstop, each near the four corners of the platform. Each lock consists of a fixed base, pneumatic cylinder (TCB50×150), crank, connecting link, rotating shaft, guide rails, slider, and a wedge block. When the cylinder extends, the connecting link pushes the slider forward along the guide rail, causing the wedge block to contact the fixed wedge block attached to the platform. The wedge angle ensures self-locking behavior and a large normal force.
A critical feature of the lock is that it must be able to withstand the lateral force due to the gravitational component of the tilted platform. The platform is not perfectly vertical because of clearances in the guide; a small inclined angle θ≈1° exists. Thus, the lock system must overcome the longitudinal component resulting from the combined mass (platform plus EV battery pack).
3.3 Guide Mechanisms
To guarantee that the platform moves vertically without horizontal drift or pitching, I designed two categories of guides:
- Horizontal guide assembly: each is a fixed plate attached to the backstop, with two guide arms and a guide wheel at the lower end. The guide wheel is spring-loaded against the side face of the platform. Three pairs are installed at different heights so that at any position, at least two pairs remain in contact.
- Pitch guide assembly: an H-beam slot on the platform engages with a guide rail that is supported by eccentric bearings. The eccentric bearings are mounted on the barrier via fixed seats. When the locking mechanism presses the platform toward the barrier, the eccentric bearings rotate slightly, allowing the platform face to align with the barrier surface. After unlocking, the eccentric bearings return to a neutral position, leaving a small clearance for free vertical movement.
3.4 Emergency Manual Release
For fail-safe operation, manual release levers are installed on both sides outside the barrier. By pulling the lever, a lifting block mechanically retracts the wedge block, thus unlocking the platform even if pneumatic power or electrical control fails. This requirement is essential in high-risk test environments.
4. Mechanical Calculations and Motion Planning
4.1 Locking Force Analysis
The total gravity of the platform and EV battery pack is:
$$
G = (M + m)g,
$$
where M = 2000 kg is platform mass, m = 800 kg is the maximum EV battery pack + fixture mass, and g = 9.8 m/s². The lateral component caused by the inclination angle θ (about 1°) is:
$$
F = \frac{(M + m) g \sin \theta}{\cos \theta}
= \frac{(2000+800) \times 9.8 \times \sin 1^\circ}{\cos 1^\circ}
\approx 478.97\ \text{N}.
$$
This is the required locking force. In other words, the lock system must provide at least 478.97 N of horizontal restraining force at each lock to keep the platform tight against the backstop. Note that the impact load from the trolley is mainly carried by the platform and the concrete barrier; the wedge locks do not absorb the impact itself but prevent the platform from bouncing off the barrier during the initial stage.
4.2 Crank-Linkage Mechanism and Cylinder Force
The locking mechanism is a crank-linkage system in which the cylinder force \(F_r\) (applied along the crank radius direction) is transformed to the slider force \(F\) at the wedge block. With the crank radius \(r\) and connecting link length \(l\) (where \(l \gg r\)), at the dead-center position the following relationships hold:
$$
F_c = \frac{F}{\cos \varphi},\qquad
F_r = F_c \cos(\theta + \varphi)
$$
$$
T = F_\tau r = F \frac{r\,\sin(\theta+\varphi)}{\cos\varphi}.
$$
When O, A, and B are aligned (dead-center), angle θ and angle φ tend to zero, so the cylinder force equals the slider load force, i.e.,
$$
F_r \approx F.
$$
Thus, the theoretical cylinder output must at least equal the locking load \(F\). In my calculation, the required theoretical force is determined using a safety factor k = 1.5 and a load rate β = 0.8:
$$
F_0 = \frac{F}{\beta} \, k = \frac{478.97}{0.8}\times 1.5 \approx 898.07 \ \text{N}.
$$
4.3 Cylinder Bore Diameter
The pneumatic system supply pressure is p = 0.6 MPa. Using the total mechanical efficiency η = 0.85, the cylinder bore diameter D is found from:
$$
F_0 = \frac{\pi D^2}{4} p \eta.
$$
$$
D = \sqrt{\frac{4 F_0}{\pi p \eta}}
= \sqrt{\frac{4 \times 898.07}{\pi \times 0.6 \times 10^6 \times 0.85}}
\approx 0.04735\ \text{m} = 47.35\ \text{mm}.
$$
To create a sufficient safety margin, I chose a standard bore diameter of D = 50 mm. The theoretical max force of this cylinder at 0.6 MPa and η=0.85 is:
$$
F_{\text{max}} = \frac{\pi \times (0.05)^2}{4} \times 0.6 \times 10^6 \times 0.85 \approx 1001.38\ \text{N} > 478.97\ \text{N}.
$$
With four locks, the total capability is about 4005 N, which is more than enough. The cylinder stroke is 150 mm, appropriate for the wedge travel distance.
4.4 Hoist Motor Selection
The platform is lifted by four wire rope branches through a set of double pulleys. The total effective weight for lifting is \(G = (2000+800)\times 9.8 = 27440\ \text{N}\).
The wire rope maximum static tension \(F_e\) is:
$$
F_e = \frac{Q}{m\,\eta_m}
= \frac{27440}{4 \times 0.96} \approx 7146\ \text{N},
$$
where m = 4 and the sheave efficiency η_m = 0.98×0.98 = 0.96 (two sheaves).
The required motor useful power is:
$$
P_w = F_1 v,
$$
with \(F_1 = G = 27440 N\) and \(v = 0.125 m/s\). Thus,
$$
P = \frac{P_w}{\eta_w} = \frac{27440 \times 0.125}{1000 \times 0.83} \approx 4.14 \ \text{kW}.
$$
I selected a ZDY131-4 conical rotor motor with 4.5 kW rated power, 1380 r/min, torque 2.7 N·m, and 380 V AC. The conical rotor motor has an inherent electromagnetic brake that prevents load drop when power is removed – a vital safety feature for lifting systems.
4.5 Wire Rope Design
I chose a 6×36WS+IWR steel wire rope with a nominal tensile strength of 1770 MPa. The minimum rope diameter is:
$$
d \ge C \sqrt{F_e},
$$
with the selection coefficient
$$
C = \sqrt{\frac{4n}{\pi k w \sigma_1}}
= \sqrt{\frac{4\times 4}{\pi \times 0.82 \times 0.46 \times 1770 \times 10^6}}
\approx 0.087\ \text{mm/N}^{0.5}.
$$
Then:
$$
d \ge 0.087 \times \sqrt{7146} \approx 7.36\ \text{mm}.
$$
Given dynamic loads and wear, I selected a diameter of 10 mm, which is a standard size and yields a higher safety factor.
4.6 Motion Speed Planning
Smooth vertical motion is crucial to avoid pendulum effects and mechanical shock. I considered three speed profiles: trapezoidal (linear), S-shaped, and sinusoidal acceleration/deceleration. The trapezoidal curve is most time-optimal but has discontinuities in acceleration that cause residual vibrations. S-curve provides a continuous acceleration but is slower. Sine-curve is elegant and smooth, providing no jerk spikes. For the hoist motor driven by the frequency converter, I implemented the sine-curve algorithm in the PLC to generate a speed reference.
For a complete lift or descent motion, the acceleration profile is:
$$
a(t)=
\begin{cases}
a_m \sin (\omega t), & 0 < t \le t_a, \\
0, & t_a < t \le t_c, \\
-a_m \sin [\omega (t – t_c)], & t_c < t \le t_e.
\end{cases}
$$
Integrating yields the velocity profile:
$$
v(t)=
\begin{cases}
v_m [1 – \cos(\omega t)]/2, & 0 < t \le t_a, \\
v_m, & t_a < t \le t_c, \\
v_m [1 + \cos(\omega (t-t_c))]/2, & t_c < t \le t_e.
\end{cases}
$$
Here, \(v_m\) is the maximum speed, and \(\omega = \pi/t_a\). Position is the integral of velocity. Using these equations, the frequency converter output ramps up to maximum speed and ramps down without discontinuities. In practice, I set different maximum speeds for normal lifting, emergency descent, and positioning motions, with additional limits for different battery pack weights. The overcurrent / overvoltage protection of the inverter is thereby respected.
5. Hardware Design and Component Selection
5.1 System Hardware Structure
The hardware is divided into three groups: servers (PC and touchscreen), controllers (PLC and distributed I/O modules), and field devices (sensors, cylinders, motor, brake, valves, and indicator lights). A comprehensive summary is given in Table 1.
| Device | Model/Description | Qty | Function |
|---|---|---|---|
| Touchscreen | Weinview MT8102iP, 10.1″ resistive | 1 | HMI operation and status display |
| PLC CPU | Siemens S7-1200 CPU 1215C DC/DC/DC | 1 | Main control logic |
| DI module | ET200SP DI 16×24VDC ST | 2 | Digital input expansion |
| DO module | ET200SP DQ 16×24VDC/0.5A ST | 1 | Digital output expansion |
| DI/DO module | SM 1223 16DI/16DO | 1 | Mixed I/O expansion |
| Communication module | CM 1241 RS422/485 | 1 | Communication with inverter |
| Encoder | Omron E6B2-CWZ6C incremental rotary + draw-wire | 1 | Position feedback of the platform |
| Proximity sensors | Omron E2E-X14MD2-Z | 15 | Limit detection and mechanism position |
| Inverter | Delta MS300 | 1 | Motor speed control |
| Hoist motor | ZDY131-4, 4.5 kW, 1380 rpm | 1 | Lifting/lowering drive |
| Electromagnetic valve | RV5322E-08 (3-position, 5-way) | 4 | Directional control for each lock cylinder |
| Cylinder | TCB50×150 | 4 | Actuation of wedge lock |
| Pressure sensor | Digital pressure switch | 1 | Monitors compressed air supply |
| Water level switch | Float type | 1 | Ensures fire-protection pool is full |
5.2 Touchscreen Selection
Given the dry and dusty laboratory environment and the requirement for operation with gloves, I selected a resistive touchscreen, the Weinview MT8102iP. Its 10.1-inch screen has a resolution of 1024×600, protection class IP65, an Ethernet interface, and three serial ports (RS232, RS485, USB). Resistive technology is preferable because it does not suffer from temperature/humidity drift like capacitive sensors, and gloves do not hamper operation.
5.3 Encoder
To determine the absolute vertical position of the platform, I used a draw-wire encoder based on an incremental rotary encoder. As the platform moves, the wire extends and rotates the encoder shaft, generating pulses. The PLC counts pulses to infer the distance. The selected unit is an Omron E6B2-CWZ6C with NPN open-collector outputs. It has three channels: A, B, and Z. Channels A and B have a 90° phase shift, allowing direction detection; Z provides a zero reference pulse per revolution.
5.4 Proximity Sensors
Inductive proximity sensors (Omron E2E-X14MD2-Z) are mounted at critical positions: upper limit, parking position, ready position, bottom position, lock/unlock positions of each mechanism, safety pin positions, and home positions. Each sensor gives a discrete 24V DC signal. Sensors provide the PLC with the exact state of each mechanical element, ensuring logical interlock.
5.5 Inverter and Motor Control
The motor is a three-phase induction motor requiring variable-frequency speed control. I chose a general-purpose Delta MS300 inverter. It communicates with the PLC via the CM1241 module using the Modbus protocol, receiving speed setpoints and sending actual status/fault flags. A separate circuit uses 380V AC from the main bus, passed through a circuit breaker and an EMC filter. The control board of the inverter is powered from a 24V DC source that is carefully isolated from the PLC to prevent electrical noise. A braking resistor is installed on the inverter to handle regenerative energy during emergency descent.
5.6 Pneumatic Circuit
The pneumatic circuit for each lock cylinder is shown schematically in Figure 2. Compressed air at 0.6 MPa enters from an air source through a filter-regulator-lubricator (air-preparation unit). Then it goes to a 3-position 5-way solenoid valve with a closed-center function, which allows the cylinder to be held in position when power is lost. From the valve outlets, two one-way flow control valves adjust the extension and retraction speeds of the cylinder. Each cylinder is double-acting. A muffler is installed at the exhaust ports to reduce noise.
The components of the pneumatic drive are summarized in Table 2.
| Component | Type/Model | Quantity |
|---|---|---|
| Air preparation unit | AEFR20004+AEL20004 | 1 |
| 3/5 solenoid valve | RV5322E-08 | 4 |
| One-way flow control valve | SL10-04 | 8 |
| Cylinder | TCB50×150 | 4 |
| Silencer | Expansion type | 4 |
| Air tubes and fittings | φ8 PU tubes, unions, tees | set |
In the event of an emergency drop, the solenoid valves for all locks are de-energized to a position that allows both cylinder chambers to exhaust, causing the wedge blocks to retract quickly. If the solenoid valve fails, a manual lever can retract the wedge mechanically.
6. Control Signal Analysis and PLC Selection
6.1 Input and Output Requirements
Based on the control architecture, the total number of digital inputs is 34. These are composed of 15 proximity sensors, 3 encoder signals, 1 air-pressure fault, 1 water-level switch, 4 panel push-buttons, and 10 remote-control button channels. The total digital outputs number 30, of which 8 are solenoid valve commands (2 per cylinder), 17 are status indicator lamps, 1 is for the ready lamp, 1 is for the fault lamp, 1 is for the inverter enable, and 2 are optional alarm outputs. The PLC also requires one analog output (0–10V or 4–20 mA) for speed reference to the inverter. In my actual design, I used a communication module (RS485 Modbus RTU) with the Delta inverter, avoiding a dedicated analog module.
6.2 PLC and I/O Modules
I used a Siemens S7-1200 CPU 1215C with onboard 14 DI and 10 DO, two analog inputs, and two Ethernet ports. For expansion, I added one Siemens SM 1223 16DI/16DO and an ET200SP distributed I/O station with 2 DI modules (16x24VDC ST each) and 1 DO module (16x24VDC/0.5A ST). The ET200SP is connected via Profinet to the CPU. The communication module CM1241 supplies an RS485 interface for the inverter. The total I/O count fits with some spare channels.
Table 3 shows a partial I/O allocation mapping for the control system.
| Address | Signal description | Function |
|---|---|---|
| %I0.0 | Encoder channel A | Position pulse input |
| %I0.1 | Encoder channel B | Direction detection |
| %I0.2 | Encoder reference Z | Zero reference |
| %I0.6 | Emergency release from control room | Immediate platform descent |
| %I0.7 | Emergency release from operator panel | Immediate platform descent |
| %I1.0 | Lock button | Engage all locks |
| %I1.1 | Raise button | Platform up |
| %I1.2 | Lower button | Platform down |
| %Q0.0 | System ready lamp (green) | Ready condition |
| %Q0.1 | Emergency release indicator | Descent triggered |
| %Q0.2 | Upper-left lock cylinder extend | Lock |
| %Q0.3 | Upper-left lock cylinder retract | Unlock |
| %Q0.4 | Upper-right lock cylinder extend | Lock |
| %Q0.5 | Upper-right lock cylinder retract | Unlock |
7. Software Design and Simulation
7.1 Development Environment
All programming was carried out in Siemens TIA Portal V18 (STEP 7 Professional). The programming languages are LAD (ladder diagram) and FBD. The program uses a main organization block OB1, a startup organization block OB100, and multiple FCs for each subsystem. Global data are stored in DBs.
7.2 Hardware Configuration
In TIA Portal, I created a new project and added the CPU 1215C (article number 6ES7215-1AG40-0XB0). Then I added the ET200SP slave and the expansion modules. The IP addresses were set within the same subnet: CPU at 192.168.0.1, ET200SP at 192.168.0.2, and the HMI at 192.168.0.3. The Profinet topology was configured, and the devices were compiled to ensure no network errors.
7.3 Control Algorithm Implementation
Representative ladder logic for the “lock” operation is shown in Fig. 4 in the form of a flow concept: The PLC first checks that the platform is at the ready position (detected by a position sensor), that the hoist is not running (up or down not active), and that no emergency release command is present. Then the lock button (local or remote) is evaluated. If all conditions hold, the solenoid valve for each lock is energized to extend the cylinder. When the corresponding proximity sensor detects that the wedge reaches the forward limit, the “locked” status is set.
The unlock operation has a similar interlock: the system can unlock only if the platform is not in motion, the emergency release is not pressed, and the safety pins are already released. Unlock-by-emergency-release bypasses most conditions to allow immediate descent.
7.4 Emergency Descent Procedure
When the emergency release is pressed (either at the operator station or in the control room), the PLC immediately de-energizes the lock valves to retract the cylinders. After all four locks are confirmed open (proximity sensors), the PLC commands the frequency converter to run at a preset emergency descent speed, say 0.3 m/s. The speed profile follows a sine ramp to avoid mechanical shock. As the platform plunges into the water pool, water resistance helps to damp the motion. When the platform reaches the bottom position, the bottom limit sensor stops the motor, and the hoist brake engages. The EV battery pack remains fully submerged for further cooling and neutralization.
If the PLC or electrical power fails, the manual release levers allow mechanical unlocking. However, the hoist brake is fail-safe: without power the conical rotor motor moves axially and presses the brake ring, preventing the platform from falling. Therefore, in a complete power failure, the platform stays in place, while manual unlocking alone would drop the platform under gravity only if the hoist brake is manually disengaged, which is a deliberate design decision. For safety, the manual release is designed so that the platform cannot fall unless a separate brake-release device is also operated. This extra interlock is described in detailed documentation but not implemented in the first version.
7.5 Sensor Signal Checking
Before the test begins, the “ready” condition is displayed. The ready condition includes:
- The compressed air pressure is above 0.6 MPa.
- The fire-protection pool water level is above the required minimum.
- The left and right safety pins are retracted (unlocked).
- All four locking mechanisms are in the locked state.
- No emergency stop has been pressed.
Only when all these conditions are met (indicated by green lamps) can the test operator request the trolley to perform the dynamic impact. During the impact, the PLC constantly monitors the voltage signals of the sensors; if any signal disappears unexpectedly, an emergency alarm is triggered.
7.6 Simulation Testing
Using S7-PLCSIM within TIA Portal, I simulated the program before physical deployment. I forced input bits to values representing locked/unlocked states and observed the outputs of the ladder logic. The simulation verified that the state transitions were correct. For example, forcing the “lock” button while the platform was in the ready position turned on the lock solenoid outputs. The simulation also revealed that if the platform was not at the ready position, the lock command was ignored, as desired. After correcting a few logic interlock errors, all test cases passed.
8. HMI Design
The HMI was programmed using EBPro in EasyBuilder Pro. It exchanges data with the PLC via Ethernet using the Modbus TCP protocol. There are three main screens: Home (main status), Parameter Setting, and Operation Guide.
8.1 Main Screen
The main screen displays the status of each readiness item (air pressure, water level, safety pin, lock states), the current platform position (in mm), the current speed, and a graphical animation of the platform. The user can see whether the system is ready. In simulation, when all the conditions are satisfied, a green indicator is shown next to each item; otherwise a red light appears. This screen also provides buttons: “Raise”, “Lower”, “Lock”, “Unlock”, and “Emergency Descend”. Only authorized operators can use the buttons, and the unlock operation is password-protected on the HMI to prevent accidental release during a live test.
8.2 Parameter Setting
This screen allows the engineer to modify velocities and acceleration times for each zone: normal raising from bottom to parking position, raising from parking to ready position, lowering to bottom (normal), and emergency descent. For instance, the speed values are input as millimetres per second. A PID or ramp generator inside the PLC uses those parameters to output the required frequency to the inverter. The parameter screen also contains the encoder calibration: the user can set the current position as a reference to correct for mechanical slack in the wire rope.
8.3 Operation Guide
The operation guide screen contains textual steps, warnings, and a flow chart. It reminds the operator to open the safety pins before attempting to lift or lower the platform. It also includes diagrams of the landing points.
9. Field Commissioning and Experimental Validation
9.1 Electrical and Mechanical Checks
After assembling the mechanical structures and wiring the control cabinet, I performed a thorough check. The control cabinet contained a main three-phase breaker, a 24V DC power supply, PLC modules, relays, and terminal blocks. The inverter was installed in a separate enclosure to minimize electromagnetic interference. Each motor cable was shielded and grounded. I used a multimeter to verify all connections before applying power, paying special attention to polarity of DC supplies and the safety grounding.
9.2 Subsystem Tests
With power applied, I tested communication between the PC and PLC through Profinet; then I used the remote control to manually force each output. For instance, pressing the “Lock” button on the HMI caused the four cylinders to extend and the wedge blocks to contact the fixed wedge. Proximity sensors confirmed the movement. Unlocking worked similarly. The raising/lowering was tested first without a battery pack at very slow speed (e.g., 10% of the setpoint). The platform moved smoothly along the guide rails, with no unusual noise or vibration.
9.3 Full System Trial
Once all individual functions were confirmed, a full-system trial was performed with a dummy EV battery pack. The dummy pack was fixed onto the platform. The platform was raised to the ready position, secured by the locks, with safety pins open. The operator started the trolley at a speed of 20 km/h. The impact head struck the dummy pack. The accelerometer on the trolley recorded a peak acceleration of about 36.8 g during 35 ms. After impact, the dummy pack showed no smoke (as expected). To validate the safety function, the operator then pressed the emergency release. The locks opened, the platform descended smoothly and immersed into the water pit. The total descent time was sufficiently short to avoid any fire risk. After soaking, the platform was returned to the parking position and the dummy pack was removed.
During the first few trials, an issue was identified when testing a heavier battery pack: the emergency descent triggered an overvoltage fault in the inverter because the motor was driven by the load and the regenerative energy exceeded the internal absorption capability. The solution was to reduce the emergency descent speed setpoint and to enable the dynamic braking resistor. After adjusting those parameters, the overvoltage fault was resolved.
9.4 Real Battery Pack Impact Test
After successful dummy trials, the system was used for an actual dynamic impact test of a real EV battery pack. In a representative test, a cylindrical impact head (d=254 mm) was mounted on a trolley with a mass of 1200 kg. The trolley hit the lateral edge of the EV battery pack at 20 km/h. The high-speed camera recorded the deformation of the pack. After the impact, the pack-side sensors indicated a rapid temperature rise in several cells. Within a few seconds, white smoke appeared at the rupture location. The operator immediately pressed the emergency release. The platform slid downward, and the pack was submerged in the fire-protection water tank. The smoke stopped, and no fire occurred. Comparison data from the sensors showed that if the pack had remained in air for another minute, it would likely have ignited. This experiment proved the value of the design.
Table 4 lists the main operation parameters obtained from a series of tests.
| Parameter | Value / Range |
|---|---|
| Trolley impact speed | 20 km/h |
| Trolley mass | 1200 kg |
| Peak impact acceleration | 36.8 g |
| Impact duration | 35 ms |
| Platform mass | 2000 kg |
| Maximum EV battery pack + fixture mass | 800 kg (designed), >1000 kg (tested) |
| Air supply pressure | 0.6 MPa |
| Lock cylinder force | ~1000 N each |
| Emergency descent speed | 0.125 m/s (later reduced to 0.08 m/s for heavy packs) |
| Total descent stroke | ~3 m |
| Water pit temperature | ambient |
10. Operational Analysis and Improvements
After several months of service, the impact explosion protection system has demonstrated high reliability. The modular design of the control program made debugging and maintenance easier. One significant improvement added later was the ability to use different speed profiles for different load ranges. The system now stores multiple profiles for lightweight, midweight, and heavyweight EV battery packs. The operator selects the appropriate profile on the HMI before the test.
Another important observation is that the wire-rope length may change slightly over time due to elastic elongation. To maintain accurate position detection, I implemented a re-zeroing algorithm using the bottom limit sensor: every time the platform touches the bottom, the encoder count is stored and used to correct any accumulated error in the position model.
The system also includes interlock logic for the “parking” position on the top floor. When the platform is parked at the topmost position, this corresponds to the stage where the pit cover can be closed after tests. If the cover is closed, the platform must not move downward unless the cover has been opened again. This prevents accidental descent onto a closed pit cover. This interlock is realized by a position sensor and a cover-open sensor.
11. Conclusion and Future Work
In this thesis work, I have developed a complete impact explosion protection system for EV battery pack dynamic impact testing. The system combines a robust fixed platform, a wedge-type locking mechanism with pneumatic actuators, a dual-direction guide system, a wire-rope hoist with variable-frequency drive, and a PLC-based control architecture. The main innovations and outcomes include:
- A new wedge-lock mechanism driven by pneumatic cylinders with manual fail-safe levers, providing fast and reliable locking/unlocking of the platform against the fixed barrier.
- A compound guide mechanism using horizontal rollers and eccentric-bearing guide rails, ensuring smooth vertical travel without horizontal drift or pitch misalignment.
- A modular, interlocked PLC program implemented in TIA Portal, with full HMI visualization and remote control, enabling safe operation from a distance.
- Implementation of sine-wave motion profiling for smooth start/stop, which minimizes mechanical shocks and prevents high thrust forces.
- Successful deployment in a commercial EV battery testing laboratory, where it has been used for real dynamic impact tests on full EV battery packs.
Future improvements could focus on the design of a universal mounting fixture to accommodate different EV battery pack geometries and reduce preparation time. Additionally, more advanced sensor fusion using temperature monitoring and gas sensors could trigger the emergency descent automatically before smoke is visible, further increasing the safety margin. Finally, a fully touch-screen based control interface might be possible, but physical buttons are still valued for fast action in emergency situations.
The project has proven that an integrated “machine—electricity—pneumatic” approach can solve an urgent industrial safety problem. This system not only enables realistic crash testing of a full EV battery pack but also ensures the safety of operators and infrastructure. My design provides a practical reference for future testing facilities and may be adapted for other high-energy storage systems undergoing mechanical abuse testing.