By Mathias Ams, Motion Control Product Manager at the Industrial Safety Systems Division of SICK AG, Waldkirch
During the setup, maintenance, and servicing of machines, staff members regularly find themselves in close proximity to hazard-ous points. The Motion Control technology therefore offers intelligent solutions for safe drive monitoring for use in these types of task. In addition to safety at the highest level, Motion Control also offers increased machine and system productivity.
In the operating environment of machines and systems, the safe monitoring of drives in various scenarios is of the utmost im-portance. The SICK Motion Control technology offers both safe and economical solutions for performing multiple safe drive moni-toring functions. It allows you to safely monitor the machine’s movement, providing safe interaction between machine and oper-ator. Motion Control offers solutions for this task. The speed and position of hazardous movements are monitored safely. Interruption in the machine cycle no longer requires a system stop, increasing productivity of the machine.
Application fields with greater safety and efficiency
Motion Control solutions are suitable for access monitoring using standstill detection and reduced speed monitoring in maintenance mode. They can, for example, be used on grinding and polishing machines. Applications include complex multi-axis machines. The technology is used to monitor end-of-line and wafer production handling machines for example. The function Safely limited speed enables you to manually intervene in machines and processes without having to stop them. Production waste can be kept to a minimum.
On automated guides systems, Motion Control solutions enable intelligent speed and direction monitoring as well as stop function monitoring. They are also used as superordinate logic controllers for protective fields covered by safety laser scanners.
Moreover, the technology is also used in machines and transport systems to monitor movement direction and system stops by acti-vating the function Safe Operating Stop. The “marriage” of the car body and chassis in car factories is an example of this kind of application, with the car body and the bracket held in position while the connection is made.
Safe monitoring of "mobile" applications
An important area of applications for Motion Control is the safe drive monitoring of mobile machines, such as automated guided vehicles (AGVs). The ideal solution for AGVs where people are able to stand in hazardous areas. Working in cooperation with safety laser scanners, it opens up new possibilities: Optimization of the monitoring of protective fields and monitoring speed and brake ramp. Encoders are centrally connected to the Motion Control module and thus enable speed and brake ramp monitoring. This monitoring optimizes protective fields, ensuring more effective use of the available space.
With the aid of the SSM (Safe Speed Monitor) and SLS (Safety Limited Speed) safety functions, the speed of an AGV can be monitored safely via an encoder on the wheels. Depending on this, the warning and protective fields of the safety laser scanners installed on the vehicle can be switched. If the warning fields are violated, the speed can be automatically and safely reduced. If a protective field is violated, the SS2 (Safe Stop 2) or SS1 (Safe Stop 1) and SBC (Safe Brake Control) drive monitoring functions intervene to monitor the vehicle safely and ensure that it comes to an safe stop.
If the controller has actioned an emergency stop for an AGV, the SDI (Safe Direction) is activated. This means that the vehicle is only able to move in one direction, thus distancing itself safely from the obstruction. SDI therefore makes a valuable contribution to structuring transport processes in a more flexible and efficient way.
Safety functions for drives in stationary machines
Motion Control is an intelligent solution for machines where physical measures are in place to keep the operator away from the hazardous point, for example machine housing, a cover or a movable guard. The advantages are: Access protection with standstill detection allows rapid intervention and maintenance and service mode with reduced speed settings to shorten changeover and setup times.
The Motion Control technology allows intervention once it has detected a machine’s standstill. Components and tools can be quickly replaced in machines secured by monitoring the drive and avoiding untinted movement. That ensures safer and more efficient operation in maintenance mode.
When working on or in a machine, for example during setup or maintenance work, SLS –safe speed-monitoring function – reduces the risk of injury. It allows for the safe monitoring of a reduced machine speed, which is necessary during setup or maintenance of a press, a wood or metal processing machine, or a gantry robot, for example, thereby enabling the user to manually reach into the hazardous area. If this speed is exceeded, it is de-tected as a fault and the machine’s drive is switched off. The ma-jor advantage of SLS reducing the speed safely is that processes do not necessarily have to be stopped. Setup processes can be completed more quickly, as the machine can be operated at reduced speed. This allows to improve the machine's productivity.
Safety when mechanical guards are open
SSM (Safe Speed Monitor) and SOS (Safe Operating Stop) are implemented functions when mechanical guards such as covers or protective doors are installed to protect hazardous points, but when the operator is regularly required to reach into the process area. Typical examples of such machines include handling systems or machine tools. To allow the operator to reach in quick-ly and safely, for example to slide out pallets or to change a work-piece or tool, the Motion Control technology initially ensures that the drive comes to a safe stop and prevents a restart. Immediately afterwards, it releases the opening of the mechanical physical guard to provide access to the hazardous point. This super-quick and safe operation considerably improves the machine's productivity and availability without delay.
In the event of an emergency, it is crucial for a machine to be able to come to a standstill. In such situations, the stop function is requested by pressing an emergency stop button, by opening a protective door or hood, which has not been mechanically interlocked, or by activating optical protective equipment. The machine can consequently be brought to a standstill in a safe and controlled manner via the SS1 or SS2 functions. If the machine fails to contact the controller or drive due to a fault, the mechanical brake can be activated via SBC (Safe Brake Control) as a final step. The Drive Monitor's SS1, SS2, and SBC functions ensure safe shutdown behavior. The advantage of this is that the shutdown time and method are known. Shorter defined stopping distance of machines can be designed optimally in terms of space and take up less room.
Distinction between safety and drive technologies offers greater flexibility
The safe monitoring of drives can be fully integrated into a safety controller from SICK – without separating or distributing the safety functions at the controller or drive level. As the concept makes a clear distinction between automation and safety technologies, machine manufacturers and integrators can handle the requests of their end customers on an individual basis, for example, regarding the drive components and suppliers to be used. This enables them to optimize costs and use the advantages of market access on a regional level. This means they do not need to rely on particular control and drive manufacturers – unlike in the case of safety integrated solutions – and allows a highly flexible response to the differing requirements of end customers.
Safe drive monitoring from a single source
Motion Control from SICK presents countless options for integrat-ed and economical drive monitoring at the highest level of safety technology. What is more, there are also sensors that are not safety-oriented, such as encoders or motor feedback systems, and can therefore provide a complete safety application, including drive monitoring, from a single manufacturer. For stationary applications, a variety of motors from different manufacturers can be used, where the motor feedback systems are already implemented. With these motor feedback systems, safe monitoring up to PL d / SIL2 with just one speed sensor – the motor feedback system – is possible, if Hiperface (safe) is used. For dual-channel structures, for example in the field of machine tools and processing machines, there are rotary encoders and linear measurement systems. In mobile applications with large pathways and measuring distances, as is common in crane systems, intralogistics, or material handling, systems consisting of encoders and distance-measuring.
This all offers you the ideal integration into the safety application, the independence from the drive system, means greater flexibility. It offers also a convenient engineering and convenient documen-tation as well as easy and fast diagnostic options. All together it’s an all-inclusive safety application solution.