The need for more complex motion profiles specific to a factory’s operations is one big reason why automated guided vehicles (AGVs) typically are used less frequently than in distribution centers. Industrial OEMs often must engineer AGVs for an end-user, and that can prove to be expensive and require longer lead times.
As the demand for specialized industrial AGVs grows, OEMs are increasingly meeting customer needs for special functionality and economy by offering standard AGV models that can be easily adapted to a wider range of factory floor applications. Equipping AGVs with such versatility is an evolving new generation of smart electric linear actuators armed with onboard intelligence and communications, extended durability, modular assemblies and flexible mounting options.
AGVs on the Plant Floor
Industrial AGVs, including carts, tuggers, self-driving forklifts and mobile robots, improve manufacturing efficiency. These machines relieve much of the human lifting involved in material transport, such as delivering materials and components to a production line. An assembly line operator at a workstation might message the need for a component to a logistics computer system.
The management system then sends the request to the AGV management software, assigning the closest vehicle to the task based on priority and motion type. After the AGV finishes the job, it signals the control system to the next step.
Much of an AGV’s work involves sliding under pallets and using actuators to raise them to transport contents wherever needed. To meet the ambitions of modern plant floor process innovation, new AGV applications demand more complex motion profiles and often require accessories such as grasping arms, claws and clamps.
Onboard Intelligence, Communications
The key to this new generation of actuators is a microprocessor and communications via an open protocol such as CANopen or SAE J1939 CAN bus. AGVs equipped with smart actuators and communications provide maximum flexibility in designing movement profiles. Getting this kind of control might have traditionally required external devices such as encoders. Today’s smart devices do it with an all-in-one solution combining software and integrated feedback devices.
The host computer knows the state, position, speed, direction and power supplied to the AGV. With such information at hand, designers can program the AGV to adapt to changing scenarios. For example, by knowing how much weight the vehicle carries and comparing it to what a plan might call for, production supervisors can evaluate the AGV’s performance.
By reading pressure from strain gauge sensors on a gripper arm, they can set it to reduce its force to prevent the gripper from crushing an object. Conversely, operators can increase the force to prevent it from dropping the object when a bump or other disruption occurs. Through real-time communication among four actuators supporting a stack of pallets, the AGV can be programmed to move only two actuators to tilt the pallet to compensate for load shifts or imbalance.
Having such detail on the AGV’s movement can also reduce maintenance costs and improve uptime. By tracking the AGV actuator and the travel distance and comparing it to the predicted life cycle, maintenance teams can reduce downtime by proactively replacing components before they break.
Mixing and Matching Other Motion Components
An actuator assembly includes a gearbox with several different gear reductions that can be adapted for load and speed, a lead screw, a nut that could have multiple capabilities, and a motor that might either be brushed or feature brushless steppers. Modern electric actuators offer more flexibility in configuring these options within the same envelope.
When partnering with a manufacturer whose can create collaboration among all engineers, the result is an actuator that meets the specific application requirements and quickly delivers a more accurate solution that also is less expensive.
If the application calls for higher speed, the designer could use a lower gear reduction. If it requires optimization for lifting force, they might use a higher gear reduction to maximize current that can adjust the voltage. If safety is a primary concern, they might integrate limit switches for an interlock design. However, one of the most significant choices impacting AGVs, is to optimize around the duty cycle by using brushless motors instead of the brushed variety.
Expanding Application Horizons With Brushless Motors
Where the brushed motor may provide duty cycles of 25%, brushless motors can deliver up to 100% duty cycles because they run without wearing down contact brushes with high current and heat. Inexpensive brushed motors are effective and useful for simpler distribution warehouse applications—though volumes are high, movements are short, simple, up-and-down strokes that do not wear down the brush material much.
For more complex operations involving frequent starting and stopping, load shifts, higher speeds and external accessories, however, a brushed motor would burn out faster than a brushless design. Whether the application requires cycling every 10 min. or millions of continuous cycles, brushless motor-driven actuators can expand the application range for AGVs.
Modern actuators provide more flexibility when it comes to mounting as well. Traditional vertical mounting is always an option, but certain applications might benefit more from a horizontal orientation that extends or retracts to control a scissor jack fixed on one side and free on the other. A vertical or horizontal mount may affect safety considerations and involve adding a foot mount on the rear of the actuator.
Another option is to use a threaded end instead of a plain rod, decreasing the overall installation length for tight design envelopes. The latter two options are available on electric actuators developed specifically for AGVs, mobile equipment and industrial automation.
Smart electric actuators, combined with modular assemblies, brushless motors and mounting options, can provide a new range of flexibility for AGVs that would not have been feasible only a decade ago. Incumbent designs could never cost-effectively deliver the necessary control, intelligence and modularity. As a result, AGVs can now go more places, do more things and bring more end-user value.
Travis Gilmer, product line specialist – Linear Actuators with Thomson Industries, supports the electric actuator business while assisting sales and customer support with technical product training.
Håkan Persson is global product line director – Linear Actuators, Thomson Industries, Inc. He is responsible for the short- and long-term strategic direction of the electric linear actuator business, including the product roadmap.
Ian Miller, P.Eng. is a national services business development Manager for Motion. He has more than a decade of hydraulic and electrical experience in the field, including system design, troubleshooting, on-site installations and technical training/support.