Technical Papers

Use in Advanced Servo Hoist Systems by Knight Global

A servo drive for all applications: Lifting loads precisely, quickly and safely with SD3

The American-based company Knight Global offers servo hoist systems that help workers in production environments to lift heavy loads. Among other industries, the solutions are in high demand among automotive suppliers - an industry that requires maximum precision, speed and, most importantly safety. The servo drive SD3 by SIEB & MEYER helps to ensure that the hoists can meet these requirements. Its open system architecture made it possible for Knight to further develop the servo drive into a customized all-in-one solution. The SD3 drive enables Knight Global to be “Industry 4.0” compliant.

Knight Global´s servo hoist systems enable controlled workload transfer by improving the precision required for the application and by increasing the speed. As an extension of an operator's natural movement, this technology greatly improves the accuracy and repeatability of an application. Unnecessary movements are avoided, response times are shortened and inertia under heavy loads has minimal impact. With Knight servo hoists operators simply pull the handle and move the load with instant response; no button pressing required.

Knight servo hoists belong to the Intelligent Assist Device (IAD) group for ergonomic material handling. They are used worldwide in a wide range of industries and are usually customized per application. "The US ‘Industry standards’ states that if an associate is required to lift more than 15 lbs. (7 kg) repeatedly for 8 hours, the employer is responsible for providing an assist device," said Douglas J. Jones, Controls / Application Manager at Knight Global. "Our emphasis is in the automotive assembly industry. We manufacture the safest hoist in the world, which include a redundant safety chain to protect against low to no maintenance."

One solution for many tasks

The SIEB & MEYER SD3 is the standard servo drive in Knight's single-axis servo hoists. As an all-in-one solution, it combines the functions of a PLC, a servo amplifier and digital and analog I/O interfaces. Background: Knight Global uses load cells in its servo hoist systems that continuously monitor the lifting loads and the up and down movement. This is the only way to ensure that the system safely controls the payload and responds intuitively to operator movements.

"The processor integrated into SD3 must correctly interpret inputs from the environment via load cells that monitor the lifting loads and up/down motion," said Douglas J. Jones. "We work with algorithms we have developed ourselves. They control the movement in order to deliver a smooth reaction by executing the proprietary motion control algorithms at very high speeds." SD3 allows these algorithms to run at the required speed, but the computing power of the product is far from exhausted. The servo drive communicates via different network protocols and interfaces with a variety of connected devices. Among other things, it hosts a user-defined website and is also integrated into Knight's universal interface software.

"Knight themselves developed the individual control program for SD3," explained Ralph Sawallisch, Key Account Manager Drive Electronics at SIEB & MEYER. "SD3 is designed as an open servo drive precisely for this purpose. In this specific case, Knight can do without a higher-level control, since the program is processed directly in the servo drive. This gives the customer a clear added value." Douglas J. Jones confirmed this: "SD3 has an open source nature which allows for exceptional freedom in creating specially tailored functionality. The Linux-based environment offers potential not found in many other platforms. From a hardware perspective, option modules offer the potential for further customization and upgrades."

Individually adaptable for a wide range of applications

With SD3 SIEB & MEYER offers a solution for complex drive tasks, e.g. highly dynamic positioning applications or servo driven nut runners and presses. It is an intelligent servo drive supplied in different power ranges up to 55 kVA. In addition, various software functions and an integrated web server are available. Option modules for a ProfiNet and an EtherCAT master interface as well as for the CANopen and EtherCAT (CoE) fieldbus interfaces are available for the SD3 servo drive, opening up a wide range of application options.

"Servo drives are often used to realize machining processes in which a large part of the know-how lies in the motion profile and the evaluation of process variables," explained Sawallisch. "With the SD3 servo drive, we provide our customers with an individual solution including a protected application area". Thanks to the function blocks supplied, the customer can focus on his core competence and independently program application solutions (e.g. in C/C++). This allows a differentiation from the competitors. SD3 has an open operating system. Thus, further customer functions and programs can be executed simultaneously, e.g. user interface, statistics, camera integration, communication and data storage. A good visualization of the process and an easy-to-understand user interface can be generated via a USB-controlled operator panel. SD3 also offers a future-oriented platform by integrating an OPC UA server to support applications in the field of IIoT.

"For us, SD3 is a product that fits our application and grows with it over time," said Douglas J. Jones. In addition to its great flexibility, the robust design of the servo drive is also an advantage for the manufacturer of servo hoist systems: Thanks to a specifically designed housing, the solution is resistant to shocks and prevents the ingress of dust and particles. In addition to the safety function STO (Safe Torque Off), the 0.5ms sampling rate is also relevant for Knight. SIEB & MEYER's consulting services were entirely convincing: "SIEB & MEYER has been responsive in supporting and continuously improving their product to meet our applications," concluded Douglas J. Jones. Heavy loads are best lifted together with a partner - or with the appropriate aids.


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