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Crane Hooks: Braking/Overhauling – Bonitron Crane & Hoist Solutions

By Materials Handling, News

Crane Hooks is a periodic update on topics related to materials handling with a particular focus on all things crane related

A motor connected to a load will be either “motoring” or “overhauling”. A motoring motor converts electrical energy into mechanical energy as is the case when a load is being lifted. An overhauling motor is driven by the load and converts mechanical energy in to electricity, acting as a generator. When the load is being lowered the motor acting as a generator is also acting as a brake for the load.

An overhauling load is creating power that, if left alone, could potentially cause an overvoltage fault in the drive. If this happens the motor will be out of control, potentially damaging the equipment being run by the motor. The overvoltage fault can be avoided by implementing either a dynamic brake or a regenerative brake. A dynamic brake or “chopper” uses transistors and resistors to dissipate the excess energy. A regenerative brake channels the energy back onto the utility grid or into a common DC Bus where it can be used by other motors.

 

When a load is lowered, the motor acts as a brake, generating electrical energy which is dissipated by regeneration or transistor/resistor units.


Transistor & Resistor vs. Line Regeneration

Braking units prevent overvoltage faults on drives. A dynamic brake or “chopper” uses transistors, which detect overvoltage situations, together with resistors to dissipate the excess energy. A regenerative brake channels the energy back onto the utility grid where it can be used by other equipment within the facility.

A dynamic brake or "chopper" uses transistors, which detect overvoltage situations, together with resistors to dissipate the excess energy A regenerative brake channels the energy back onto the utility grid where it can be used by other equipment within the facility
Dynamic Braking

The dynamic brake method typically has a lower up front cost, but heat generated by resistors can increase cost two ways. If the resistors are indoors, added cooling capacity may be required for the room. Large resistor banks may be kept outside, far from the drive, but this results in more wiring and conduit cost. Resistors also need time to cool down after a braking cycle. Regen units are rated for continuous use and so are typically a better choice for high duty applications such as cranes and hoists where utility power is used.

A dynamic brake or "chopper" uses transistors and resistors to dissipate the excess energy. A regenerative brake channels the energy back onto the utility grid or into a common DC Bus where it can be used by other motors.
Line Regeneration

Line regen solutions have many advantages. First, because the unit does not generate high levels of heat (99% efficient), it can be integrated into the drive cabinet. Second, the unit can run continuously without the need of a cool down period. Third, the lack of heat generation allows its use in environments where there might be flammable materials such as feathers, dust, or wood. The regen also boost energy efficiency as it puts electricity back into the AC line where it can be used by other equipment, considerably reducing the demand from the utility.

Both

A regen is most effective for frequent or continuous braking up to 450A, while a transistor/resistor is more suited to higher peak loads for shorter durations. If necessary, transistor/resistor and regen units can be used together for a more efficient solution, where the regen handles continuous braking needs and the dynamic brake activates when the regens’s capacity is surpassed.

Transistor/resistor and regeneration units can be used together for a more efficient solution

Source: Bonitron Crane & Hoist Solutions | 615-244-2825

Crane Sentry® Hook Height by Laser-View Technologies

By Crane positioning, Editor's Choice, laser distance sensor, Materials Handling, Sensors

Crane Sentry Hook Height featuring Dimetix laser distance sensors includes a laser remote module and laser monitoring gateway

Does anybody ever really know exactly how high the hook is at any point over its course of travel or how hook height changes under differing loads at different extensions? Maybe at certain reference locations, but the truth is, not really. The thing is, safety adjustments or corrections to ensure level operation under heavy load cannot be made without that information. Meet Crane Sentry® Hook Height by Laser-View Technologies–without it you can’t really know. Our solution includes the right Dimetix laser distance sensor for the intended application, a laser remote module and laser monitoring gateway.

For more information on Crane Sentry Hook Height or any of the other members of the Crane Sentry family of laser distance sensor-based overhead crane position and collision detection monitoring systems, please visit our Website at www.laser-view.com, call 610-497-8910, or email us at [email protected].

Vision-guided autonomous vehicles give Giant Eagle a lift – Network World

By Automated storage and retrieval system (ASRS), Editor's Choice, Materials Handling, News

Wheels turning and forklifts filled—that’s one measure of success in any warehouse. If you can increase the amount of product picked up and put away, the more productive and cost efficient you are.

For Pittsburgh-based retailer Giant Eagle, the key to making that happen is to operate vision-guided autonomous vehicles—robots—in its distribution centers.

By eliminating manned travel of pallet trucks in its Pittsburgh and Cleveland grocery distribution centers, Giant Eagle increased productivity between 10 percent and 30 percent, said Joe Hurley, senior vice president of supply chain at Giant Eagle.

The company operates between two and four Seegrid vision-guided autonomous vehicles in each facility per day, per shift. They’re used to haul freight from the front dock (inbound freight) to the particular aisle where a manned high-lift vehicle then puts the product into a reserve rack. And they do this continually 24/7.

Each warehouse is like a mini city, Hurley explained, with robots, manned vehicles and pedestrians (105 to 120 workers, depending on the shift) all working in the same space.

“In Pittsburgh, it’s a 440,000-sq.-ft. distribution center that has 28 aisles, about 32,000 pick and reserve slots and holds about 8,000 stock keeping units,” he said. “And the robots are integrated with our different team members. There are no segregated aisles. They’re integrated into the workflow with the team members operating double-pallet jacks, single-pallet jacks or high-lifts.”

Further, each center does outbound distribution the same time it does inbound. It does not have dedicated receiving shifts or dedicated selection shifts.

“It’s almost like controlled chaos,” Hurley says.

Controlling the chaos while maximizing productivity

The functionality of the Seegrid vehicles helps keep the order and allows for maximized productivity, said Jeff Christensen, vice president of product and services at Pittsburgh-based Seegrid. Unlike traditional, automated guided vehicles that use in-ground guide wires, paint on the floor, or reflectors and are restricted to specific paths, Seegrid’s vehicles can travel anywhere in a warehouse. Companies do not have to modify their infrastructure to operate them.

“We’ve taken a different approach. We take pictures,” he said.

Each vehicle has five stereo-pair cameras that operate similar to human eyes. With each pair, the cameras are a known distance apart from each other, and they take pictures at the exact same time. The slight differences between the two cameras (its eyes) tells the vehicle how far away something is—gives it depth perception.

“Taking pictures from these five pairs of cameras allows us to have thousands of points in three-dimensional space at every moment along the way as the vehicle drives,” Christensen said.

In a vehicle’s initial use, a worker guides the truck through the facility and the vehicle takes pictures all around it, including the floor and ceiling. It finds data from those images and records it. It maps the facility.

“There’s nothing you have to put in the facility. You don’t have to change the infrastructure at all. You just take pictures,” Christensen said. “Then when you effectively hit ‘play,’ from what you’ve recorded, it takes those pictures again and compares what the camera sees to what the cameras saw earlier. And that is how it can navigate and drive autonomously.”

This video shows how Seegrid’s autonomous, vision-guided vehicles operate in one of Giant Eagle’s distribution centers:

Because of the amount of data the cameras pull in, the vehicles are able to adjust to most changes, Christensen said.

“We have sufficient data that allows us to be very robust to a lot of changes in the environment,” he said. “On average, half of everything in an environment can change, and we can still navigate.”

If an environment changes enough that the robot won’t work, customers can retrain the vehicle in the segment where the change is and the vehicle rebuilds the map from there.

Maximizing productivity and reducing costs

Each vehicle has sensors to gather data. And all of the data—such as the size of the load picked up, how long it takes to deliver the load, where the vehicle is in the facility, vehicle downtime—are uploaded to the Seegrid Supervisor application. Hosted on site or in the cloud, the app allows customers to track metrics, issue alerts if there’s a problem with the vehicle and adjust the environment if needed.

For example, factory managers need to know how many items vehicles moved. They use takt times, such as “The loop to move from my warehouse to the start of the assembly line and back needs to be completed every 43 minutes to keep my production standard.” Managers need to know if the vehicle is within that accepted timeframe. The Seegrid Supervisor can help them track that.

“Those operation metrics are really important,” Christensen said. “Once you go from manual movement and manual driving to autonomous, you gain in predictability of what’s being moved when. It’s a huge economic benefit.”

Hurley confirmed that his facilities have seen improved productivity using the vision-guided vehicles and the data they gather.

“We know everything about what the robots are hauling, how they’re hauling it, the number of routes they do per day,” he said. “We know that when wheels are turning and forks are filled, we’re taking manned travel out of the facility. Our high-lifts alone travel about 600 miles a day. So, as much as we can take that 600 miles and make them automated miles, with improved productivity, it’s good for us.”

The data also helps ensure the robots operate in the most efficient ways possible.

“You don’t want to flood the robot, nor do you want to starve the robot. So, for example, the data taught us how to … keep the robot fed in a steady pace” to prevent downtime, Hurley said.

Hurley was also able to prevent congestion in aisles.

“We did that with our high-lifts because you don’t want to have 10 high-lifts in a certain aisle because you’re receiving paper all day,” he said. “The robots allow us to define that even more.”

Preventing accidents

Sensors on robots also prevent accidents—something Giant Eagle’s workers were particularly concerned with when the company decided to bring in the vision-guided, autonomous vehicles, Hurley said.

They have a laser-based sensor—the failsafe sensor near the floor—to detect personnel. And another laser-based sensor specifically for other obstructions that come into play.

“We call it a light curtain,” Christensen said. “We bounce a laser off of some mirrors to bend the light down, creating a curtain around the truck, so it sees other obstructions in addition to a person who is walking to it.”

The vehicles also sound a horn at the end of an aisle to alert workers that it is entering the main aisle of the warehouse.

Hurley said Giant Eagle’s workers, which are part of the Teamsters Union, needed convincing that the freely roaming vehicles were safe. The company had previously used a system in which guide wires were put into the concrete floor and vehicles traveled a specific path.

“We had to make the workers feel comfortable working with unmanned vehicles that weren’t in a tight environment,” Hurley said. “We had to get the workforce to understand that the safety curtains would work.”

Workers had to get comfortable knowing that if a person gets into that zone, or if the vehicle is programmed to take a turn, it will reduce its speed. And if anything gets into the vehicle’s path, it will stop.

Hurley said the robots are very predictable, and their controlled features make them safer than human-operated vehicles.

“The robot doesn’t make decisions like a human where it will veer off path to pass someone or take a shortcut to beat the labor standard,” he said. “When something gets in front of it, it will stop. It won’t try to think and make an alternative move that may hurt someone.”

After thousands of hours operating the Seegrid vehicles, Giant Eagle hasn’t had one injury caused by them, Hurley said.

Future-proofing their environment

It’s a six-figure investment to purchase a Seegrid vehicle, but the economic payback in large factories and warehouses is “well under two years—often under one year,” Christensen said. It’s flexible automation that reduces the cost of materials handling and allows customers to keep using the vehicles should their manufacturing process and facility change.

“If you are investing in a tool that could be used in the process today and could be used for the process tomorrow—whatever that is—then you are future-proofing automating your environment. That’s another future economic benefit,” he said.

The vehicles also help reduce costs for things that are considered non-value-added, such as material handling, Christensen said.

“If manufacturers can be more cost-effective in their material handling, then that is healthier for the whole plant,” he said.

Hurley said some workers were initially concerned their jobs might be replaced with automated vehicles. But they saw what the robots were doing to protect the interest of the company in the long term. Also, they have learned new skills, such as how to maintain the robots.

“We have an interesting workforce,” Hurley said. “We’re a large regional player, but our folks understand if we don’t introduce new technology, we’ll go by way of the dinosaurs.”

What IS an Encoder? – Robotics Tomorrow (press release)

By Automated storage and retrieval system (ASRS), Editor's Choice, Fabrication and metalworking, Food processing, Industrial automation, Manufacturing, Materials Handling, News, Sensors

Encoders use different types of technologies to create a signal, including: mechanical, magnetic, resistive and optical – optical being the most common.

Contributed by | Encoder Products Company

A VERY basic introduction

If you Google encoder, you’ll get a vast and confusing array of responses. For our purposes,encoders are used in machinery for motion control.

Encoders are found in machinery in all industries. You’ll find encoders used in cut-to-lengthapplications, plotters, robotics, packaging, conveying, automation, sorting, filling, imaging, and many, many more.  You may have never noticed them, but they are there. In this blog post, we will give you a very basic introduction into what an encoder is, and what it does.

Encoders in use

Encoder

What IS an encoder?

Simply put, an encoder is a sensing device that provides feedback. Encoders convert motion to an electrical signal that can be read by some type of control device in a motion control system, such as a counter or PLC. The encoder sends a feedback signal that can be used to determine position, count, speed, or direction.  A control device can use this information to send a command for a particular function. For example:

  • In a cut-to-length application, an encoder with a measuring wheel tells the control device how much material has been fed,  so the control device knows when to cut.
  • In an observatory, the encoders tell actuators what position a moveable mirror is in by providing positioning feedback.
  • On railroad-car lifting jacks, precision-motion feedback is provided by encoders, so the jacks lift in unison.
  • In a precision servo label application system, the encoder signal is used by the PLC to control the timing and speed of bottle rotation.
  • In a printing application, feedback from the encoder activates a print head to create a mark at a specific location.
  • With a large crane, encoders mounted to a motor shaft provide positioning feedback so the crane knows when to pick up or release its load.
  • In an application where bottles or jars are being filled, feedback tells the filling machines the position of the containers.
  • In an elevator, encoders tell the controller when the car has reached the correct floor, in the correct position. That is, encoder motion feedback to the elevator’s controller ensures that elevator doors open level with the floor. Without encoders, you might find yourself climbing in or out of an elevator, rather than simply walking out onto a level floor.
  • On automated assembly lines, encoders give motion feedback to robots. On an automotive assembly line, this might mean ensuring the robotic welding arms have the correct information to weld in the correct locations.

In any application, the process is the same: a count is generated by the encoder and sent to the controller, which then sends a signal to the machine to perform a function.

How does an encoder work?

Encoders use different types of technologies to create a signal, including: mechanical, magnetic, resistive and optical – optical being the most common. In optical sensing, the encoder provides feedback based on the interruption of light.

Illustration of the parts of encoders

The parts of an encoder

The graphic at right outlines the basic construction of an incremental rotary encoder using optical technology. A beam of light emitted from an LED passes through the Code Disk, which is patterned with opaque lines (much like the spokes on a bike wheel). As the encoder shaft rotates, the light beam from the LED is interrupted by the opaque lines on the Code Disk before being picked up by the Photodetector Assembly. This produces a pulse signal: light = on; no light = off. The signal is sent to the counter or controller, which will then send the signal to produce the desired function.

What’s the difference between Absolute and Incremental encoders?

Encoders may produce either incremental or absolute signals. Incremental signals do not indicate specific position, only that the position has changed. Absolute encoders, on the other hand, use a different “word” for each position, meaning that an absolute encoder provides both the indication that the position has changed and an indication of the absolute position of the encoder.

For more detailed information on how encoders work, see WP-2011: The Basics of How an Encoder Works, and the Encoder Basics section of EPC’s Installation and Wiring Guide.

 

About Encoder Products Company
Encoder Products Company (EPC) is a leading manufacturer of premium rotary incremental and absolute encoders used for motion feedback. Our encoders are available worldwide to OEMs, MROs, End Users, Service/Repair Organizations and others through a qualified network of electrical, motion control, and industrial distributors. The Americas Division of EPC, located in Sagle, Idaho, USA, is headquarters for worldwide manufacturing and encoder research and development. To service and support regional markets, EPC also operates manufacturing facilities in Europe and Asia.