An Introduction to Rigging Automation

Monday, June 26th, 2017

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This article originally appeared in the Spring 2017 issue of Professional Lighting & Production magazine

By Mark Desloges & David Bond

We’ve all seen it; the demand for rigging automation is growing. As an increasing number of largeformat productions incorporate these incoming technologies into their shows, we seem to want more and more of this latest craze for more modest events and tours. But what is automation, really?

Let’s break it down to its basic elements, discuss some possibilities and potential applications, and touch on how we can safely utilize these systems.

WHAT IS IT?

In its most basic form, automated rigging is the practice of pre-programming the movement of set elements, like a truss, for example, on an axis in physical space. Sounds simple enough, right? But let’s look a little closer.

When I first started training on automated rigging systems, I had a narrow view of what automation was. Like most practical applications in the Canadian live entertainment market, I focused on chain hoists that can move a piece up and down with repeatable accuracy. Typically this would be a lighting truss or a video wall; however, this is a very narrow view as automation has so much more potential.

When I say “axis,” I’m referring to a movement along a line. By definition, an axis is a theoretical line that divides something into two parts – top and bottom, left and right, near and far – for the purpose of stage movements.

These are the three basic axes that an object can move along:

  • Vertically (in/out)
  • Horizontally (stage left/right)
  • Through the depth of field (upstage/downstage).

An object can also rotate around these axes, resulting in tilt, pitch, and rotation (see Fig. 1).

FIG. 1

FIG. 1

 

It’s important to note that there is usually more than one way to achieve these movements, be it a chain hoist, a wire rope winch, a rotating turntable, hydraulic rams, trucks, or a beam trolley. The available hardware to automate is often not the limiting factor – typically, it’s your budget or imagination.

HOW IT WORKS

To automate a machine, it needs to be able to make repeatable movements, be programmable, and in the entertainment world, have a cue system for control during the show. To do this, we need measurable data from the machinery itself. Measuring rotations of a machine is a common way to know if it is moving, in which direction, at what speed, and how many rotations have been made.

So let’s focus on automated chain hoists as a typical show element. Now, there is a common misunderstanding with regards to “intelligent” chain motors. We often describe these as having a “link counter” system, meaning something is counting links of chain as they are processed through the motor. What is in fact going on is an encoder inside the hoist is sending data to the control software pertaining to how many rotations are made by the machine, in which direction, and in some cases, at what speed.

To take this a step further, automation requires encoders for positional data. An encoder can be mounted on almost any piece of moving hardware, one way or another. As long as you can make a gear or shaft turn and you can attach an encoder to it, you have a way to measure the rotation and therefore make use of the data it provides.

So here’s how it works. Automation is designed and controlled on the front end by consoles and computer-driven systems, much the same as lighting systems. These controls are integrated into different hardware systems via energizing power drives or switches, like a motor distro or a winch drive, and then process data from sensors such as encoders. The software energizes machinery on cue and acquires data from the encoder so it can tell the machine when to stop in a specific position.

Programming these systems can be done in a number of ways and there are lots of different platforms and approaches, so let’s talk basics.

Every manufacturer has their own way of accomplishing the end goal of programming moves in the form of cues. It could a table-based system where you enter values based on the desired travel distance and speed/time. It could be CAD-based, where you build a 3D construct in virtual space and the system does more of the calculating for you. Or it could be something more sophisticated like a 3D flight path console with joy-stick interfaces. As with most product families in our industry, the approach changes with each manufacturer. Akin to learning a new sound or lighting console, there is most certainly a learning curve involved and, typically, training required.

The basics of automation can be taught to a competent technician with ease in the right environment. It is important to remember, though, that what you do in the virtual space can have serious implications in real life.

Muse's concentric pyramid video screen automated on variable speed hoists with link to media servers, enabling image mapping according to screen position.

Muse’s concentric pyramid video screen automated on variable speed hoists with link to media servers, enabling image mapping according to screen position.

HOW YOU CAN USE IT

Being an arena rigger by trade, I always thought in terms of chain hoists when I first started training in automated rigging. “What could I do with all of those hoists?” was what I was thinking. What I wasn’t thinking about was the bigger picture. While hoists typically cover movement along the Z-axis, let’s focus our attention towards other practical applications.

Winches are a popular tool for faster or more powerful moves but they are most often used for Z-axis movement, as are chain hoists. There are lots of different capacities of winches and some are capable of creating much more force or power than a standard entertainment chain hoist. Being able to generate incredible speeds and high torque, they can be used in a wide variety of applications to provide accurate, smooth pulls along one axis. This can be seen in many formats, from architectural installs to theatres to high-speed camera movements in film to actually flying performers.

Trolleys are a practical way to accomplish movement along the X and Y axes – specifically upstage/downstage and stage left/stage right. This is often accomplished via an electric motor that is mounted to a track. The motorized trolley has a rigging point that can be moved along this track by applying power to the drive.

Furthermore, you can compound your axis by rigging a hoist to the bottom of your trolley. As your trolley tracks along an X or Y axis, the secondary system can move up and down along the Z axis, giving you a compounded axis with many more options for movement.

The last axis of movement is rotation. This is accomplished via rotators, devices that spin, tilt, or rotate an object around an axis. This could be a simple rotator on a point that allows it to spin, such as a mirror ball, or it could be as large as a circular section of staging that spins inside the outer staging. There are even examples of large-format stages with an inner rotating circle that has a ground-supported structure in the middle. This centre section rotates, changing the position of the downstage point of reference of the stage itself. This is an awe-inspiring effect when used in a 360-degree environment, or in a more familiar term, “playing in the round.”

There are two basic forms of automated rigging equipment: fixed speed and variable speed systems. Both have their practical applications, but the key word here is speed. Speed is what determines how the force is applied by a motor that is energized as it starts, runs, and stops.

In physics, this is described by Newton’s second law of motion and the formula F=ma, which can be translated to: force in Newtons is equal to the weight in kg, times acceleration in m/s2. Or, 1 Newton = 1 kg times m/s2.

Let’s look at this in a practical sense. The heavier your object is and the faster you move it, the more force you generate. If you take a heavy video wall and move it with a high-speed motor, you will put a lot of force on your rigging when it changes speed. Heavier objects should be moved at slower speeds unless the systems and supporting structures are capable of safely dealing with the forces they can generate.

Now, taking this full circle, fixed speed automated motors are an economical way to provide show moves. Variable speed motors enable faster and smoother movements. This is accomplished by ramping the acceleration and deceleration of the motor providing the movement. By curving the rate of the beginning and end of the move, you are able to better control the force applied. This ramping reduces the shock load on your rigging by starting slow, accelerating to speed, making the move at speed, and then slowing down gradually before the brake is applied to stop the movement.

It’s just like adjusting the amount of pressure you apply to the accelerator of your car as you take off, or before you apply the brakes. If you have the pedal to the metal right up until you hit the brakes, the deceleration will be harder than if you slowly let off it before applying the brakes. You can also apply the brakes gradually to slow down before coming to a stop. This initial braking is done electrically in show automation, which reduces the velocity of an object before the machinery’s brakes stop the movement. Keeping these simple physics in mind can make a huge difference in the safety of your system. Bear in mind that even if a system can provide a smooth ramp, the emergency stop or a loss of main power supply will engage the brakes immediately, causing an instantaneous stop and high dynamic load.

U2's 360 Tour "Video Funnel," motion controlled with variable speed winches and approx. 40 variable speed chain hoists. [Photo Courtesy of Kinesys]

U2’s 360 Tour “Video Funnel,” motion controlled with variable speed winches and approx. 40 variable speed chain hoists. [Photo Courtesy of Kinesys]

HOW TO KEEP IT SAFE

To safely operate automated rigging systems, one must be well versed in the basics of entertainment rigging and the mechanics of motion.

It is easy to get carried away with the power of automation. With such bountiful opportunities and clients with eyes so wide, it’s easy to push limits. Understanding these limits is the key to safe operation.

Modern systems have many built-in failsafes to keep the operator well within the safe working capacity of their rigs; however, if you don’t know the basic rigging principles, you’re at great risk of making a catastrophic mistake.

Design your rig and systems from the ground up, remembering that the entire show depends on your weakest link. All your safety precautions will be for nothing if you don’t correctly attach your automation to the truss or video wall and whatever supports it. You must know the safe limits of your venue and your equipment, so plan thoroughly. Getting it right the first time is essential.

Like all forms of entertainment rigging, your success starts at the top. Fully understanding what the capacity in a particular venue is, how to properly rig there, and how to correctly install your rigging, including bridling, is crucial. If your basket up top is incorrect, then anything you do below that will be incorrect. Whether you are attaching your automated hardware directly to the roof, via a mother grid system, on a fly rail, or any other variation, you must understand the working limits of your particular situation. Understanding and working within these limits is the best way to produce movements that are not only visually stunning, but also safe.

Let’s talk more about limits. Limits are ways to keep your rig within its safe working parameters. There are soft limits and hard limits.

Soft limits are programmed into the software and are dependent on your encoder. This is a value you program based on a zeroing of your rig to match your virtual space and the physical space. If your lower soft limit is programmed at a distance that is below your stage in physical space, and you write a cue to go to that position, you’re going to have a bad day. Conversely, if your upper soft limit is higher than an obstruction, you will drive your rig into whatever is in its way. These limits are crucial for working within a safe boundary.

On the other hand, rigging hardware like hoists, and winches, and trolleys will have hard limits. These are mechanical limits in the form of switches that can remove power from the contactor, restricting the available direction of travel at an electrical level. In a hoist, the hard (or mechanical) limit is just what you think it is – the same hard limit that you are used to with a conventional fixed speed hoist. This is typically a shaft attached to the hoist’s drive that has a travel plate. As the hoist moves up and down, the plate spins to one side of the shaft or the other. When it reaches a certain point, it will make contact with the limit switch, cutting power to that direction of travel.

Hard limits usually won’t change, but your soft limits will. It is of great importance that as you build your automated system, you measure and program these soft limits to ensure you don’t try to program a cue that could cause a collision.

Other limitations to consider are speed clamps to limit the velocity of travel, load detection to limit the amount of force a system will exert, and safety precautions such as remote emergency stop switches, “deadman handles” to assure the move is being authorized by a spotter, etc.

Light switches and curtains can avoid unsafe movements just as an electric garage door can be stopped if a beam of light is interrupted in the doorway. Some control software systems even feature collision avoidance for constructs in a virtual 3D environment. There are CSA standards for industrial automation and the same principles apply here. If there is a risk or danger, the system must be designed to eliminate or mitigate it. This could be redundant components checking each other, secondary brakes, and higher safety design factors for life-safe critical elements.

Finally, let’s talk about dynamic loads. In conventional rigging, you are calculating a static load and compensating for shock loads as you start and stop travel. In automated rigging, you are dealing with potentially higher dynamic loads due to heavy objects that are in motion more frequently and at potentially higher speeds compared to standard machinery.

These loads are much more complicated to calculate as an object moves, and in the real world, this is something that is not easily done on paper. Because of this, higher end systems have introduced integrated load cell systems to provide feedback, and they combine that information with encoder feedback. These systems offer a higher level of safety if not just for the reason that you are able to monitor the applied loads, but many systems can use this data to automatically avoid overloads. There is a large gap between calculating dynamic loads the old-fashioned way and real-time accurate load monitoring.

Being as keen for safety as I am, I always suggest the consideration of load cells in automated rigging systems. There is a lot to be said about the difference between guesswork and hard facts.

OPTICAL ENCODERS

There are many types of encoders, but let’s focus on a commonly used variety in stage automation: the optical encoder.

This is a common electro-mechanical component that houses a glass disc with opaque and clear sections around it, like a bicycle wheel or a pie missing every other slice. As it spins, light passes through the glass disc and a sensor sends electronic pulses when it sees changes in the light. The software then interprets these pulses.

Because we are able to count the number of pulses per revolution, we are able to tell how many times the encoder has turned and associate that value with a measurement in physical space. The more pulses that you can read per revolution, the more accurate your encoder will be. This is called encoder resolution.

The reasoning behind this is that you can divide one revolution of your mechanical turn, or physical distance traveled, into a larger number of pulses per full revolution, resulting in more data and better accuracy. We also need to establish how many pulses are read for each measurement of physical distance (chain processed). This is called scaling and can be done with a measuring system and some calculations.

IN CLOSING

The entertainment industry is known for pushing the boundaries of technology. Entertainment designers are often at the forefront of new audio and visual technology and automation is no exception. I am excited for the future of entertainment rigging, and I look forward to the opportunity to work with more automated rigging systems.

As a market for automation, Canada has had huge success with the export of largescale, high-budget automation shows, but the era of more accessible and mid-scale automation is just around the corner. It is no longer just Cirque du Soleil and arena-sized concert tours using this technology; now, theatre productions, mid-market tours, and more can put this powerful and potentially spectacular technology to use.

*****

Mark “The Drifter” Desloges is a freelance touring rigger. He has travelled across North America with acts like Johnny Reid and productions like Let It Be. He is also a climbing rigger for IATSE Local 680 and can be reached at markthedrifter@gmail.com.

David Bond is Head of Sales, North America, for Kinesys USA.

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