Select the Appropriate Power Supplies for Cobots and AGVs in Manufacturing

Automated manufacturing increasingly relies on collaborative robots (cobots) and automated guided vehicles (AGVs) to improve production efficiency and reduce product variability. Cobots work in close proximity to human workers and are generally lighter and smaller than traditional industrial robots. They also handle lighter payloads, move at slower speeds, and apply lower forces. AGVs, on the other hand, move within a facility, ferrying materials and packages. Both have distinct power challenges.

Cobots are typically powered by an AC/DC power supply that must meet their dynamic power demands. These demands vary with load weight, speed, and movement complexity. AGVs are battery-powered and require rapid charging to minimize downtime. This necessitates charging stations with sufficient power for fast charging.

Both applications need reliable, efficient, and appropriately certified power supplies.

This article examines the unique power challenges facing designers of cobots and AGVs in industrial manufacturing automation. It then presents solutions from Advanced Energy and highlights the features that help designers meet these requirements.

Power requirements for cobots and AGVs

The key requirements for cobot and AGV power supplies include compact size, reliability, high power output, and robust protection against short circuits, overloads, overvoltage, and overtemperature. They must also meet electromagnetic compatibility (EMC) requirements to minimize interference with other devices and comply with basic electrical and physical safety regulations for users and surrounding equipment.

The power source for cobots must handle highly variable power demands because the power requirements vary with the load the cobot must move, the complexity of the movement, and the required rate of change. Additionally, the cobot may need to operate multiple joint motors simultaneously. This requires power supplies with a high maximum power capacity. Due to the limited space within the cobot, the power source must be as small as possible, which requires high power density. Industrial and factory automation environments run 24/7, demanding high reliability and a long mean time between failures (MTBF). Also, the highly variable power loading requires power-supply control-loop dynamics that remain stable regardless of load variations and frequently harsh environmental conditions.

AGVs transport materials and goods autonomously, without human supervision. Equipped with sensors and vision systems, AGVs reduce human error and improve efficiency and safety, lowering the risk of workplace accidents. Typically battery-powered, AGVs require fast, unobtrusive charging stations to minimize disruption and downtime.

At a time when innovation and time-to-market are key to success, cobot and AGV designers often lack the resources to cost-effectively design and develop a suitable power supply. Instead, they need access to a broad portfolio of reliable power solutions backed by technical expertise, enabling them to focus on application differentiation rather than power supply development.

Advanced Energy LCM1500 series power supplies

Designers of cobots and AGVs can turn to Advanced Energy's LCM1500 series (Figure 1) of AC/DC power supplies to meet the performance, reliability, efficiency, and safety requirements of manufacturing automation. The LCM1500’s leading-edge circuit design, including digital feedback control, combined with carefully selected components and automated production processes, yields high-performance, cost-effective power supplies. This broad line of power sources also offers a variety of options and custom configurability.

Figure 1: Examples of the LCM1500 power supply configurations show both the terminal block (left) and blade (right) output connections. (Image source: Advanced Energy)

The LCM1500 is available with standard output voltages of 12 V, 15 V, 24 V, 28 V, 36 V, and 48 V for a variety of manufacturing automation applications. For example, cobots routinely use 48 V supplies to provide a common DC power bus, which is distributed to individual motors at each movable joint. The output voltages in the LCM1500 supplies are adjustable over a ±10% range, and have a set-point tolerance of 0.5%. The LCM1500 supply is enclosed in a 2.5 × 5.2 × 10 inch (in.) housing intended for chassis mounting. The 1,500 W output power rating in this enclosure yields an output power density of 12 W per cubic in.

High power densities like this require forced-air cooling. In these supplies, cooling is provided by dual ‘Smart Fans’ mounted on the rear panel of the power supply. Fan speed is controlled by software that adjusts it to meet the cooling requirements. The front panel is perforated to allow cooling airflow, while the remaining enclosure walls are solid. The 2.5 in. height of these power supplies makes them a good fit for installation in 2U rack enclosures.

Units with higher output voltages have a heavy-duty terminal block for connecting the output. The 12 V and 15 V units, which have output currents of 100 amperes (A) or greater, provide blade contacts.

The LCM1500 series power supplies are rated for operation over a temperature range of -40 to 70°C, with the output power linearly derated above 50°C and limited to 50% full power at +70°C (Figure 2).

Figure 2: Shown is the temperature derating curve for the LCM1500 series power supplies. (Image source: Advanced Energy)

The power supplies in the series have a calculated MTBF greater than 300,000 hours, based on the Bellcore 332, issue 6 specification (+25°C and +40°C ambient, at full load). Under normal operating conditions, the product family has an MTBF of greater than 500,000 hours, based on performance data.

These supplies operate over an input voltage range of 90 V_AC to 264 V_AC with power frequencies from 47 Hz to 440 Hz. Their input power factor is typically 0.99, and their input surge (inrush) current is limited to 25 A.

Total voltage regulation, including line, load, temperature change, and warm-up, is 2% due to digital feedback control. These supplies can share output current, allowing up to 10 supplies to be connected in parallel to increase output power.

Protective functions to look for

LCM1500 series power supplies feature multiple protection functions. These are necessary for applications such as cobots, where a jammed motor can draw excessive current from the power supply. The key functions to note are:

• Overvoltage protection (OVP) shuts down the supply in the event of output overvoltage. It protects AGV batteries from overcharging during a power fault and is cleared by cycling the AC input.
• Overcurrent protection (OCP) is an internal circuit to limit current in the event of an overload or short circuit. OCP automatically attempts recovery approximately 20 second (s) after overload removal.
• Short circuit protection (SCP) protects all outputs in the event of a short circuit to ground or to another output. As with OCP, the output is restored 20 s after the short circuit is removed.
• Over-temperature protection (OTP) shuts down the power supply when the ambient temperature exceeds +55°C under full load. OTP self-clears when the temperature falls to a safe value.
• The power supplies are protected by a 30 A fuse in the AC input lines. The fuse is internal and not user serviceable.

Two status LEDs on the front panel indicate the presence of AC power (ACOK) and report the state of the DC output as either functioning (DCOK) or in shutdown mode (FAIL) (Figure 3).

Figure 3: A view of the LCM1500 front panel shows the location of the status LEDs and the primary connections. (Image source: Advanced Energy, modified by Art Pini)

When the power supply is functioning normally, these LEDs are on and show green. In the event of failure, they are off. The key front-panel input, output, and control connectors are also shown.

PMBus simplifies power supply management

The industry-standard PMBus is an I²C-based communication protocol for managing power supplies. PMBus works with all types of power-management products, including AC/DC power supplies. The LCM1500 series includes an I²C interface port accessible via the signal connector. This enables monitoring and control of the power supply via PMBus commands, including powering on or off, monitoring status, setting the output voltage level, and more. The remote-control function is useful for enabling interactive control of robotic devices, such as putting the supply into standby mode to reduce power consumption when the cobot is inactive.

Standards certifications

The LCM1500 series meets electrical safety, EMC, and international regulatory requirements for industrial automation applications, including certifications per IEC/EN/UL 62368-1 and related standards (Figure 4).

Figure 4: Shown is a summary of LCM1500 safety, EMC, industrial, medical, and international regulatory certifications and approvals. (Image source: Advanced Energy Industries)

The design of the LCM1500 series also ensures compliance with FCC Part 15, CISPR 32, EN55022, and relevant sections of EN61000 (IEC 61000) for immunity. These requirements ensure electromagnetic compatibility (EMC) in the factory environment, where multiple RF sources and receivers must coexist.

LCM1500 power supply options and configurations

The LCM1500 power supplies are available in a variety of configurations to help designers meet application requirements.

Consider the LCM1500Q-T-4, which has a 1500 W, 24 V nominal output voltage and a maximum current output of 67 A. It also has an optional built-in 5 V standby power bus capable of supplying up to 2 A for auxiliary circuits. The standby power is available via the 20-pin control connector.

The LCM1500W-T-B is a 1,500 W front-end power supply with a single 48 V output and a maximum output current of 33 A. It includes two options: reverse airflow and constant current. Reverse airflow reverses the standard rear-to-front airflow; instead, air is drawn in through the front panel and exits through the rear-mounted fans. Constant current maintains the output current at a fixed level by varying the voltage.

The last model is the LCM1500Q-T-5, a 1,500 W, 24 V supply with a maximum current of 67 A. It includes the 5 V standby power option and features conformal coating on all the circuit boards.

The conformal coating protects the boards against moisture and particle contamination in industrial environments.

Conclusion

Cobot and AGV designers need dependable power sources that deliver high power in compact, factory-compatible form factors. Advanced Energy’s LCM1500 series power supplies deliver 1,500 W of output power, with a range of output voltages and optional features, making them ideal for cobot and AGV systems in manufacturing environments.