Q. How are the challenges of safe motion being addressed by Pilz?

A. First, there are two sides to these types of operations:

1. The safety from the motion component side (i.e. robot, drive, etc.) verifying what motion is occurring
   
2. The external feedback for these components (i.e. what's going on in the immediate environment)
   These two components determine how the motion component should act in regard to changes in its environment. For example, as an operator approaches a robot, it should reduce speed, change its position to perform an operation away from the operator or stop to a safe stat in order to eliminate any hazard it poses to the operator.
   

With regard to Pilz products, we're designing safe motion into our PMC drives, including features such as safe stop and safe speed. We've also developed a safe area monitoring device called SafetyEYE, which monitors the immediate area in 3D, supplying control signals to the motion device when an object enters the area. This provides the feedback necessary to slow, stop or change the motion in order to adapt to a changing environment.

Q. Are there any changes to the definition of machines covered under the new MachineryDirective?

A. There are a number of refinements and additions to the definition of a machine. The core definition of a machine is now:

An assembly, fitted with or intended to be fitted with a drive system other than directly applied human or animal effort, consisting of linked parts or components, at least one of which moves, and which are joined together for a specific application.

A machine must have a "drive system" such as an electric motor, linked parts one of which moves, such as a mechanical slide and must be constructed to perform a specific application, such as molding a plastic part or welding two parts together.

Q. What types of industries would benefit most from safemotion? Example of a possible scenario where humans can work closer to robots?

A. Any industry with direct human/process interaction. Typical applications in assembly would be part loading, part inspecting/gauging, welding or preventative maintenance of the cell/application. An example of a load operation with a robot would include the following process:

1. Operator loads work piece onto table and steps away
2. Robot picks up the piece and holds it for weld, or welds it on the table
3. Robot moves away or places piece back on the table
4. Operator removes the welded piece and places a new one on the table

With safe motion, the work table could essentially be removed, allowing the operator to place the work piece directly on the robot end effector. This would, remove a large physical barrier (i.e. the table) from the work area, as well as eliminate several steps from the operation.

Q. What challenges or hurdles still need to be addressed with safe motion.

A. The standards provide the performance criteria for more sophisticated applications, but there are still many opportunities to implement the more complex applications that are now permitted. In robotics, the most challenging applications involves systems that continue to operate in the present of operators. The collaborative operating mode of maintaining a safe distance between the robotic arm and the operator is yet to be realized. Also, yet to be achieved, is the mode of operation in which the robotic arm force, torque and momentum is limited to inherently safe levels.

The advantage of safe motion, is that it allows the user a closer proximity to the actual process. With safe motion (whether it's safe speed, position or torque), if you can guarantee that the robot/drive is doing exactly what it's intended to (ie. working in a restricted space, at a restricted speed or is at stop), you can reduce and even eliminated your "safe distance" requirements. This would allow the operator to essentially work hand-in-hand with the motion component, increasing production time, reducing floor space and giving the operator a more friendly & ergonomic working environment.

Q. How do safe motion systems work? What role does advance motion control technology play?

A. Reliability theory has been applied to adjustable speed drive technology to define the reliability required for safety applications. There is an acceptance in industry for concept of integrity levels. Higher CPU power, reliability of components and a high level of diagnostics to detect dangerous faults before a failure can prevent a safety function from occurring has allowed these functions to be realized. Application of redundancy and diversity to complex control systems provides a means to predictable and acceptable failure rates.

What happens if a worker is injured as a result of safety defect on a machine?

Many factors come into consideration in answering this question. The new Machinery Directive requires member states to implement penalties that are effective, proportionate and persuasive. However, it is up to each member state to decide on the appropriate penalties. Other national laws may come into play in relation to civil or criminal prosecutions. It should be understood that the "Product Liability Directive" applies in cases where a product "does not provide the safety which a person is entitled to expect."

What is the concept of safe motion? How does it apply to robotics?

Safe motion is the capability of providing motion control functions at an integrity level high enough to reliably provide risk reduction in safe dependent applications. An integrity level is the measure of the predicted failure rate of a control function. Risk, the possibility of harm in relationship to the potential degree of severity, must be reduced to a tolerable level in a safety application. A given integrity level ensures the possibility of harm occurring is sufficiently reduced to be tolerable for a safety related function. These integrity levels and design requirements are now defined in IEC 61800.

Safe motion extends the safeguarding of hazardous motion beyond the traditional dropping of power to the motors when personnel are exposed to a hazard. With safe motion, these are some of the new safe functions available by allowing power to continue to flow to the drives and to the motors:

• Safe torque off
• Safe controlled deceleration to a stop
• Safe operational stop (safe stand still)
• Safely limiting speed or torque
• Monitoring a position or maintaining a speed 

Protective measures implemented in traditional control systems such as reduced speed and hold-to-run functions can be further enhanced through this higher integrity.

In robotics, new applications are now available to the user. The international standard ISO 10218, for robotic safeguarding, is defining new applications for safe motion.

Setting safety related axis limits and defining safety zones in three dimensional spaces is allowing easier reduction of the restricted space of a robot to provide maximum clearance while minimizing the work cell.

ISO 10218 allows for collaborative operation between the robot and the human. In this application the robot may be allowed to stay in automatic, with power available to the motors and possibly continue its motion. The robot may safely limit its speed and if necessary top in a safe standstill mode (safe operational stop) while the operator works on a part in the robots gripper. A safe operational stop is characterized by the halting of motion, but keep torque output on the motors to resisting external forces. Coupled with sophisticated presence sensing technology, all the variations of this application have not been thought of yet.

Is this the only directive impacting suppliers and users of machinery?

No. There are a number of other directives, many dating back to the 1980's, that you need to be aware of. When creating the single market, the social partners agreed that protection of the Health, safety and Welfare of workers was a key value within the community. This led to the enactment of the "Council Directive 89/391/EEC of 12 June 1989 on the introduction of measures to encourage improvements in the safety and health of workers at work."

Another important directive is "Council Directive 89/655/EEC of 30 November 1989 concerning the minimum safety and health requirements of the use of work equipment by workers at work" (and subsequent amending directives 95/63/EC and 2001/45/EC). This directive impacts employers who use machinery and sets out minimum requirements for existing machinery and requires that all new machinery should meet the requirements of all applicable directives, including the machinery directive.

Q. Did the original directive result from the creation of the single market in Europe?

A. Yes, the single market depended on the elimination of barriers to trade between member states and enshrined protection for the freedom of movement of capital, people, goods and services. The Engineering and Machine building sectors were and are important sectors of the European economy. However, prior to the first machinery directive there were no common regulaions or standards for machinery supplied on the market. The aim of the EU in introducing the Directive 89/392/EEC and it's amending Directive 98/37/EC, generally known as the "Machinery Directive", was to ensure the free movement of the products within the scope by guaranteeing a high and common level of protection in the areas of health, safety and consumer rights.

Why Did the European Commission Create a New Machinery Directive?

A.
As with all laws drafting is not perfect and the commission recognized gaps between the effects that were intended and achieved in the original drafting. A commissioned study by a high level group of independent experts into the practical application of the machinery directive resulted in the "Molitor Report". This report issued in November 1995 contained 12 recommendations for simplifying the application of the Machinery Directive. Most of these recommendations have been followed in Directive 2006/42/C. The objectives in introducing a new directive are to: provide a better definition of key concepts within the directive, to clarify certain aspects and requirements which were perceived as ambiguous, to ensure uniform application, to consolidate and simplify the application of the directive in harmony with other EU directives and to provide greater legal certainty for buyers and suppliers.

Motion Control for Packaging Machines

In today's competitive atmosphere, shorter innovation cycles and flexibility are vital to packaging companies wanting to rise above the competition. We are continually hearing from machine builders and Original Equipment Manufacturers (OEMs) about these challenges and the complexities they bring to machine operator safety and the pressure to do this efficiently.


Further, this demand has resulted in the decrease of batch build and multi-pack runs and now requires machinery to produce multiple packaging variations from the same machine. Adapting to this means the ability to perform quick product changeovers while maintaining a high level of throughput productivity.

Ultimately this impacts the machine operator's ability to perform quickly and safely. This reality has driven the industry to look into alternative solutions. Automation, coupled with motion control is the key to accomplishing this. However, the increase in motion requires a robust safety system to monitor and control these added moving components. For safety processes to run quickly and smoothly systems require multiple axis controllers, additional motion control devices and they must meet industry standards.

When these modified systems are deployed properly you will achieve the required flexibility and observe an increase in the throughput of products. One last issue to accomplishing this is choosing the right safety products to fit system needs.

When looking for motion control products it is important to look at the overall picture. First of all, motion control is needed to manage the movement of any highly dynamic drives and camshafts, synchronization of a wide range of decentralized drives to keep manufacturing safe at a low cost and at a consistent quality. Second, quick setup and maximum flexibility, as well as the ability for automatic adjustment to product variances are essential. Finally, the handling and robotics of a packaging machine is as an integral part of a complete automation solution.

Any and all motion control products must include the following: PLC to control the machine, optimum movement management on decentralized drives for motion control and an individual safety solution customized with integrated software and tools that meet universal, local and federal legislations.

Packaging specific applications and motion control components should also be adaptable for individual requirements. The ability to join together safety and industrial standards is a crucial element in any motion application. Equally imperative, safety must be integrated within the drive to make sure that every law of motion is available, optional real or virtual master axes and all additional tools able to suit the task of a specific packaging machine.

It is important to note, that a control solution should also be platform-independent. Integrated soft PLC in accordance with IEC 61131-2, can fast scan time from < 50us for 1000 instructions and no adjustments are required to change platforms. Thus, all of the automation in one project with support for modular structures, large selection of field buses, extensive libraries, motion control, interpolation and OPC Server, can positively impact both safety and productivity.

In further examining comprehensive motion control functionality, always consider this indispensible checklist to discern the most important features within any motion control product:

• Virtual main shaft and cam synchronization

• Integral "flexible cam"

• Register control

• Web tension control

• Linear and circular interpolation

• Electronic camshaft and safe motion within the drive

When choosing safety products for your packaging machines choose a company that is aligned with your priorities and use the above checklist to ensure you're making the best choice possible.