News USE 2 Years Design a truly plug-and-play, all-servo motor integrated drive and control box

Project Background:
Since coming into contact with game emulators in 2023, I have been thinking about a question: motion simulators on the market are either expensive and bulky commercial simulators or personal DIY products with poor performance and complex installation, debugging, and after-sales service. Moreover, the price and performance of personal DIY products depend on the individual's understanding of motion control and servo drivers, leading to huge price differences. It is almost impossible for individual players to find a product with good performance, reasonable price, and portability. Why not design one myself? Based on this idea, I wanted to design a high-performance, compact, plug-and-play, and expandable integrated drive-control box during my spare time. I shared this idea with my friends who specialize in software design and structural design, and they responded positively. The main reason is also to leverage more than a decade of R&D experience in industrial automation to create a product for individual consumers. I have 15 years of hardware R&D experience in industrial automation, having designed and mass-produced motion controllers, PLCs, and servo drivers. My partner also deeply participated in the design of the first-generation prototype of Oculus. If you need to use this power box for industrial automation applications such as 3D printers, laser cutters, desktop CNC machines, robots, or other scenarios requiring high-precision multi-axis control systems, you can also contact us. We will assist you in how to use this power box correctly.

Project Implementation
1: Determine the Scheme
Motion Controller Scheme Determination
Most products on the market commonly use Arduino development boards, and the quality of the experience mainly depends on the controller's performance. Motion decoupling is done using SimTools and FLYPT on the host computer. The advantage of this approach is that the controller program is simple, but the disadvantage is that complex motion planning and algorithms critical to the experience cannot be implemented on the lower computer, leading to severe homogenization. It becomes very difficult to create innovative experiences. After careful consideration, STM32F407ZGT6 from ST was ultimately chosen. While this chip has slightly weaker performance for industrial control, it should be sufficient for game simulator applications requiring maximum motion planning at 2ms.
Interfaces:
USB *2 Planned for LOG port and host computer communication port (optional)
Ethernet Host computer communication port (default)
RS232*1 Planned for expansion peripherals
RS422*1 Host computer communication port (optional)
CAN2.0*1 Reserved
2.4G WIFI Reserved
2.4G BLE Mobile phone communication
DI x 8 8-channel DI input (NPN)
Do x 8 8-channel DO output (NPN), single channel current limit 200Ma
Limit x 6 6-channel limit input, each supporting positive and negative limit
EMG Emergency stop input

2: Servo Solution Determination
it is a home-use product, safety is the top priority. decided to use 48V servo drives. The advantages of low-voltage servos are as follows:

1) Safety: Industrial multi-axis high-pressure servo systems may have leakage issues when operating for a long time under conditions where the user grounding is not good.
2)The power density can be made very large.
3) It can be powered by batteries

Servo Parameter Determination:
Bus Voltage: 48V
Encoder: A 17-bit single-turn absolute value motor with Tamacon protocol is selected, which is also compatible with multi-turn absolute value motors.
Current Sampling: High-precision Δ-Σ modulator oversampling is adopted, and software algorithm filtering is used, which can achieve extremely low carrier frequency noise. The advantage is ultra-quiet operation.
Driver Protect
Overcurrent Protection:
Overcurrent protection is implemented by setting the overcurrent point through software design. It is adjustable on the host computer.
Overload Protection:
Overload protection is achieved through software settings, and it is adjustable on the host computer.
Short Circuit Protection:
Considering that if short circuit protection is not timely, it may burn the circuit board. The short circuit tolerance time of general MOSFETs is 2us-10us. The time from the occurrence of a short circuit event to the shutdown of the wave is limited to within 2us, which can protect the MOSFET from damage during short circuit. Therefore, two types of shutdown methods (hardware and software) are designed. When a short circuit occurs, hardware shutdown is performed first, followed by software shutdown.
Undervoltage Protection:
it is adjustable on the host computer software.
Overvoltage Protection:
The default opening voltage for software braking is 80V, closing at 70V, with a hysteresis of 10V. It can also be set through the host computer software. An internal brake resistor is built-in. The actual test shows that when the load is 150kg, the temperature rise is not high.
Overtemperature Protection:
The overtemperature point is adjustable on the host computer, and the temperature near the heat source can be read in real time.
Heat Dissipation:
Through two 8025 dual-bearing fans with adjustable speed via software. Considering that the internal environment is not enclosed, blowing air is more effective for heat dissipation than suction.

Considering that the product may also be applied in industrial environments or battery-powered environments, the entire system has been designed for low power consumption.

Rated current of 400W motor
400/48*1.414=11.8A Overload 3 times, approximately 33A
Rated current of 750W motor
750/48*1.414=22A Overload 1.5 times, approximately 33A
Single-axis hardware overcurrent setting is 31A. When exceeding 31A, hardware wave blocking will be triggered, providing short-circuit protection and overcurrent protection in case of software loss of control.

3D Diagram of the Control Panel

BACK

3D diagram of the driver board
Front

Back

Drive protection waveform

Figure 1: Yellow represents the U-phase lower bridge arm waveform of the MCU output, red represents the Vgs waveform of the MOS lower bridge arm, and green represents the Vgs waveform of the MOS upper bridge arm.

Figure 2: The yellow waveform represents the short-circuit signal generation, and the red waveform represents the PWM enable shutdown. Δt=54ns. The time from the occurrence of the short-circuit event to the hardware wave blocking time t is 1.3μs + 0.054μs = 1.354μs, with a short-circuit current of 31A.

Figure 3: Over-temperature protection waveform. The over-temperature point is software-adjustable, with a default value of 100°C.

Figure 4: Undervoltage Protection Waveform. In abnormal conditions, when the voltage drops to the set value, PWM hardware and software wave blocking is triggered. The default value is 15V, mainly to ensure compatibility with 24V voltage.

3: Housing Design
Dimension Diagram:





Internal Structure Diagram

6-axis test 1
Motor: 750W
Electric cylinder: Stroke 200mm, Lead 10mm, Connection method: Directly integrated

6-axis testing 2
Motor: 400W
Electric cylinder: Stroke 120mm, lead 5mm, connection method: folding platform type

4-axis test platform: In processing

Hi David
I was getting excited to think I was almost on page two then it just stopped.
Will we be getting the next installment soon

Force Analysis of Servo Actuator:
Suppose the maximum load is 200kg, maximum acceleration is 2m/s², and the lead screw pitch is 10mm.
Step 1: Calculate total thrust F
F = Lifting force + Friction force + Acceleration force
Lifting force = Mass × Gravity = 200kg × 9.8 m/s² = 1960 N
Friction force ≈ 50N (empirical value, guide friction)
Acceleration force = Mass × Acceleration = 200kg × 2 = 400N
Total thrust F = 1960 + 50 + 400 = 2410N
Step 2: Calculate required total torque T
T = (F × P) / (2 × π × η_s) = (2410 × 0.01) / (2 × 3.1416 × 0.9) ≈ 4.26 N·m
Step 3: Add safety factor
Final total torque = 4.26 × 1.5 ≈ 6.39 N·m
Motor end torque for 6-axis platform: 6.39 / 6 = 1.065 N·m
Motor end torque for 4-axis platform: 6.39 / 4 = 1.5975 N·m
Step 4: Select motor
For the 6-axis platform, select a servo motor with rated torque ≥ 1.065 N·m.
For the 4-axis platform, select a servo motor with rated torque ≥ 1.5975 N·m.

400W servo motor, rated torque 1.27 N·m, peak torque 2.54 N·m


750W servo motor, rated torque 2.39 N·m, peak torque 5.7 N·m


For ball screws with a 5mm lead, the required torque will be halved. In fact, for 400W and 750W servo motors, short-term 2x overload (e.g., 5 seconds) will not affect the motor's service life. The main factor influencing motor heating is the long-term average current.

Step 5: Verify the lead screw life.
The dynamic load at the end of the lead screw for the 6-axis platform is 2410/6 = 401N.
The dynamic load at the end of the lead screw for the 4-axis platform is 2410/4 = 602.5N.


Conclusion: For 4/6-axis platforms, a 400W servo motor can meet the requirements. If cost allows, a 750W motor would be better. Since SIMTOOLS and FLYPT drive the motors based on position planning, the 1605 lead screw has a lower rated current and higher acceleration, while the 1610 lead screw has a higher rated current and lower acceleration. The 1610 lead screw allows for longer travel and a larger range of motion. Personally, I recommend choosing the 1610 lead screw.

V. Power Supply Capacity Design
The required power supply capacity depends on the lifting speed. The basic calculation formula is as follows:
1. Lifting force = Mass × Gravity = 200kg × 9.8 m/s² = 1960 N
Friction force ≈ 50N (empirical value, guide rail friction)
Accelerating force = Mass × Acceleration = 200kg × 2 = 400N
Total thrust F = 1960 + 50 + 400 = 2410N
2. Lead screw lead: P = 10 mm = 0.01 m.
3. Torque (considering lead screw efficiency η_s): T = (F × P) / (2π × η_s).
4. Motor speed: To ensure the motor bearings operate stably and reliably for a long time, the maximum speed is set at 3000 rpm / 60 = 50 rps, resulting in a maximum lifting speed of 50 × 0.01 m/s = 0.5 m/s. If the motor overspeed alarm occurs, this parameter can be increased.
5. Mechanical power: P_mech = T × ω = T × (2π × v) = (F × v) / η_s, where η_s is the lead screw efficiency.
6. Motor input electrical power: P_in = P_mech / η_m, where η_m is the motor efficiency.
7. Total efficiency η_total = η_s × η_m, so P_in = (F × v) / η_total.
8. Power supply voltage 48V, required current I = P_in / 48.
Therefore, the power supply capacity should be greater than P_in. Assuming typical values: lifting speed v = 0.5 m/s, lead screw efficiency η_s = 0.9, motor efficiency η_m = 0.9, then total efficiency η_total = 0.81.
P_in = (2410 N × 0.5 m/s) / 0.81 = 1205 W / 0.81 ≈ 1487 W.
I = 1487 W / 48 V ≈ 31 A.
31 A × 1.5 = 46 A
All the above calculations are based on the maximum operating conditions. The designed power supply capacity only needs to sustain for 5 seconds under this condition to ensure stable operation in the worst-case scenario.

Power Adapter Dimensions






The CE, UKCA, and FCC certifications for the electrical box are in progress. If any friends are interested in this product, You can add me on WeChat.