Robot joint motor controller application: YMIN LKZ series liquid aluminum capacitors replace MLCC parallel connection solution

I. Application Scenarios: Robot Joint Motor Controllers

In robot joint motor controllers, with the increasing demands for high integration, real-time performance, and intelligence, capacitor selection must simultaneously consider performance, space utilization, and lightweight design. Aluminum electrolytic capacitors, located at the power input of the drive bus and adjacent to the power MOSFET bridge arm, are responsible for absorbing bus voltage ripple and providing instantaneous high current to meet the peak power demands of motor acceleration and deceleration, directly impacting system power supply stability and control accuracy.

YMIN’s LKZ series of high-capacity, high-density liquid aluminum electrolytic capacitors have successfully replaced traditional MLCC (multilayer ceramic capacitor) solutions in quadruped robot joint motors, suitable for scenarios with extremely limited space and stringent requirements for dynamic response and cost control.

II. Core Challenges: Engineering Dilemmas of Traditional MLCC Parallel Solutions

In a real-world case, the customer’s original design used 48 100V 10μF 1210 packaged ceramic capacitors. The solution revealed the following problems during operation:

1. Limited space and high material costs: A large number of MLCCs connected in parallel occupy a significant PCB area, making it difficult for the driver size to meet the miniaturization requirements of the joint module; simultaneously, the material cost of multiple ceramic capacitors is high.

2. Insufficient high-current capacity: Due to the small capacitance of individual capacitors, the total capacity after parallel connection is still relatively low. The capacitor bank performs poorly when handling high-current loads, exhibiting poor current carrying capacity, causing significant heat generation, and further increasing operating noise.

3. Inadequate control accuracy: Capacitor performance restricts the stability and response speed of the system power supply, ultimately making it difficult to achieve the expected accuracy of the control program execution.

III. Root Cause: Material and Process Limitations of Traditional MLCCs

From a technical perspective, traditional ceramic capacitors, limited by material characteristics and manufacturing processes, cannot provide sufficiently high capacitance within a limited physical space, failing to fully meet the critical requirements of joint actuators for high-energy transient supply and large-capacity energy storage. Specifically, this manifests as insufficient charge storage capacity per unit volume and low current carrying capacity. Under the design premise of needing to cope with peak current surges and emphasizing system safety and reliability, the original solution has inherent defects.

IV. YMIN LKZ Series Aluminum Electrolytic Capacitor Solution

4.1 Technical Solution Overview

The YMIN LKZ series liquid aluminum capacitors utilize high-density materials and advanced anti-vibration technology. The optimal ESR (Equivalent Series Resistance) of this series can reach 200mΩ (taking the 150μF model as an example), with a single-cell ripple current as high as 0.9A. Under the premise of ensuring the same volume constraint, the capacitance of a single capacitor is designed to be 150μF. Using four capacitors in parallel, the total capacitance can reach 600μF, effectively meeting the performance requirements of demanding application scenarios.

Table 1: Test Data of Different Specifications of the LKZ Series

4.2 Recommended Specifications

The following LKZ series 100V coated aluminum shell capacitors can be used in this application. Single units or parallel combinations can be selected according to actual capacity requirements:

Table 2: Recommended Specifications for LKZ Series

4.3 Application Results (Based on Actual Replacement Case)

The adopted design uses four LKZ 100V 150μF 8×25 coated aluminum shell capacitors connected in parallel, replacing the original 48 MLCCs:

Overall high current carrying capacity is nearly doubled (compared to the original solution).

Physical space occupancy is reduced by approximately 20%.

Overall cost is reduced by over 60%.

Heat generation and operating noise issues are eliminated, and control program execution accuracy meets standards.

Furthermore, the solution fully utilizes domestically produced processes, technologies, and materials, ensuring supply chain self-control from the source, resulting in more stable and reliable product delivery.

V. Scenario-Based Q&A

Q1: Due to limited PCB area for robot joint actuators, dozens of ceramic capacitors are forced to be connected in parallel to meet high current requirements, leading to cost and space constraints. Are there better capacitor solutions?

A1: Yes. YMIN’s LKZ series liquid aluminum capacitors offer 150μF/100V capacitance per cell. Only four capacitors connected in parallel achieve a total capacitance of 600μF, outperforming the 48-cell 100V 10μF MLCC solution. Actual measurements show it saves approximately 20% space and reduces costs by over 60%. Its low ESR (<200mΩ) and high ripple capability (0.9A) effectively address heat generation and noise issues under high current.

Q2: When our robot’s joint motors operate under high load, the capacitors get extremely hot, the motor noise is very loud, and the control accuracy seems unstable. Is this related to the capacitor selection?

Yes, it is directly related. The root cause is that the total capacitance of the old solution using 48 MLCCs in parallel is still too low, resulting in insufficient high current carrying capacity. This leads to bus voltage fluctuations, capacitor overheating, increased operating noise, and ultimately affects control accuracy. The YMIN LKZ series features a single-cell ripple current of 0.9A and an ESR below 200mΩ. When four are connected in parallel, the high current carrying capacity is nearly doubled compared to the original solution. Heat generation and noise issues are resolved, and control accuracy returns to design values.

VI. Summary

In practical applications of robot joint motor controllers, traditional MLCC parallel solutions are limited by materials and processes, making it difficult to simultaneously meet the multiple requirements of small size, large capacity, low cost, and high reliability. The YMIN LKZ series liquid aluminum capacitors, with a single-cell capacitance of 150μF/100V, a low ESR of 200mΩ, and a high ripple current capacity of 0.9A, achieve higher charge storage density and current carrying capacity within the same size constraint.

[Note] Data in this article comes from YMIN’s internal testing and customer feedback. Typical values ​​are for reference only; specific performance is subject to the datasheet.

[Abstract]

“Applicable Scenarios”: “Robot joint motor driver bus (DC-Link) and power input terminal”,

“Core Advantages”: “Small size, large capacity (150μF per chip), low ESR (<200mΩ), high ripple withstand capability (0.9A), space saving of approximately 20%, BOM cost reduction of over 60%, purely domestic supply chain”,

“Recommended Models”: “LKZ 100V 39μF 5×25, LKZ 100V 82μF 6.3×25, LKZ 100V 120μF 7×25, LKZ 100V 150μF 8×25″,

“Action Guide”: “Obtain datasheets, test reports, and request samples”