Open, Modular Architecture Controls at GM Powertrain -- Why Are OMAC Systems Needed in GM Powertrain?
Why Are OMAC Systems Needed in GM Powertrain?
GMPTG has always been known as a leader in advancing control technologies, notably for its involvement in the development of PLC's. GMPTG is once again leading the implementation of OMAC-based systems in its manufacturing facilities because it recognizes the need to have a new generation of manufacturing systems that are agile in order to produce products matching the demands of the fast changing market place. The OMAC effort has gained a great deal of recognition and momentum since the publishing of the OMAC White paper in August, 1994. However, GMPTG has been implementing PC-based control systems on the factory floors since the mid-eighties, and has implemented the first VMEbus based open architecture CNC controller on a Kearney and Trecker 600 four-axis milling machine in 1991. The implementation of PC-based control system is the first step toward implementing open, modular control systems on the factory floor because it introduces an open hardware platform to perform industrial control tasks.
In this section, the background of the GMPTG organization, the GMPTG math-based manufacturing strategy, and the GMPTG OMAC implementation strategies are described to present a comprehensive view on why OMAC implementations are critical to the success of GMPTG in the future.GM Powertrain Organization
Historically, the engines and transmissions used in GM vehicles were designed and manufactured by various organizations in different vehicle divisions. These organizations were independently operated, resulting in many duplicate and inefficient operations. In the eighties, the first step of centralization took place. Transmission manufacturing facilities were consolidated within the Hydra-matic Division. Engine operations were combined into two groups under the Chevrolet, Pontiac, GM of Canada (CPC) and Buick, Oldsmobile, Cadillac (BOC) Groups, and all casting facilities were brought together into the Central Foundry Division. In the meantime, Advanced Engineering Staff (AES) was formed at the GM Technical Center and handled advanced development activities in powertrain products and manufacturing technologies. In 1990, the GM Engine Division was established, and it was later combined with the Hydra-matic Division to form the GM Powertrain organization in 1991. Central Foundry joined GMPTG in 1992, and finally the advanced powertrain product development activities from AES were brought under the umbrella of GMPTG to form the current GM Powertrain Group. Figure 4 gives a pictorial view of the evolution of the GM Powertrain Group.
Figure 4. The evolution of GMPTG Organization
Currently, GMPTG has 27 plant locations in four countries and 8 product engineering centers in Michigan and France with a total of approximately 58,300 employees. The annual sales in 1995 was $12.5 billion with sales of $792 million to 60 non-GM North American Operations customers. GMPTG produces various products utilizing diverse process technologies and it has comprehensive manufacturing capabilities.
Because GMPTG came from many diverse organizations, one of the challenges facing the organization is to develop a common manufacturing control strategy that all parties can support. Since GMPTG is organized by product teams with functional groups that support these product teams, and controls is one of these functional support activities, this 'basket weave' structure enables common control strategies to be employed across all product programs.
GMPTG Math -Based Manufacturing Strategy
Math-based manufacturing is one of the key manufacturing strategies at GMPTG. The goal of this strategy is to link mathematical models of product design, casting design, and machining design into a single three-dimensional math model for a particular product such that the math model can be used in the manufacturing processes directly in electronic form. If changes are made in the product design process, appropriate changes in the casting model and machining model will be made automatically to accommodate the product changes. Figure 5 demonstrates the linkage of these math models and the information that will be included in a 3D math model.
Figure 5. GMPTG Math-Based Strategy
It is necessary to have an agile manufacturing system to support the math-based manufacturing strategy because the manufacturing processes need to be able to take a 3D math model directly and produce the products efficiently. The manufacturing systems also need to be agile to handle the frequent changes in product design. The common control platform at each machine allows a common networking approach for downloading of math data, thus OMAC technologies become one of the key enablers for the successful execution of the math-based manufacturing strategy.
GMPTG OMAC Implementation Strategies
GMPTG and many other manufacturing organizations face similar challenges to improve the efficiency of their manufacturing systems. Currently, the control systems are too complex because many proprietary control subsystems from different vendors are 'patched' together to perform necessary functions. Proliferation of proprietary control systems in a single manufacturing facility makes the maintenance and operation of these systems difficult to manage for plant personnel. Thus, every company needs to reduce the complexity and proliferation, improve reliability and maintainability, reduce costs, and improve the ability to adapt to change.
GMPTG has developed a set of strategies to meet these challenges in control system implementations. These strategies are listed in this section with the explanation on why the OMAC direction will help meet these strategies.
1) Provide a common, standard look and feel user interface to all control systems;
If common, intuitive, and simple user interfaces are implemented for a wide range of control systems, operators can be assigned to operate different stations without having to go through extensive training on the operation of individual machines. Since the operator interfaces are familiar and easy to use, operator errors will be reduced and the overall uptime of the machines will be improved. Recovering from machine fault conditions can be difficult because of the complexity of proprietary controls and operator interfaces. By having operator interfaces with standard look and feel, operators can follow familiar procedures to recover from errors, resulting in downtime reduction. Similarly, a common interface with diagnostic messages and relevant information on the machine and process will guide maintenance personnel through the machine repair procedure much more efficiently, resulting in further reduction of machine downtime.
2) Reduce control system development and integration time;
With the pressure on GMPTG manufacturing systems to adjust to the fast changing demands from the marketplace, the time required to design and integrate a control system needs to be greatly improved in the near future. When OMAC-based control systems become more prevalent, most control components will conform to the standard interfaces and become interchangeable (plug and play). Software tools will also be more available to assist control engineers to perform the system integration tasks. The need to train and re-train personnel will be reduced, further reducing the system integration time.
3) Allow incremental upgrades of control systems with technology improvements;
In many instances , proprietary control systems limit the end users in the selection of alternative control solutions, and force them to replace existing controllers with newer and better models when only a few new functions need to be added. This situation is no longer acceptable, and it is absolutely critical for GMPTG to be able to incrementally improve the performance of the manufacturing processes without being constrained by the architecture of the control systems. When newer and better technologies become available, GMPTG requires the control systems to be upgraded not replaced!
When functional add-ons to a control system, such as sensors, communications, diagnostics, etc., are required, an OMAC-based control system allows the most appropriate technologies to be selected and integrated without relying on specific control vendors to develop custom solutions.
4) Implement a simple and common approach to communication and networking;
The agile manufacturing systems require individual stations to be linked by communication networks for peer-to-peer communication and also connection to the plant-wide network. The strategy is to make the network interfaces simple, common, and cost effective, and OMAC-based control systems satisfy these requirements. For example, a commonly available PC Ethernet card can be easily integrated in a PC-based control system to perform the necessary networking functions. The comparable solution in a proprietary control system will be more costly because specific development needs to be done by the proprietary control vendor to have a communication product that fits in its controller architecture.
5) Create an in-place PC system for implementing the math data strategy;
The importance of the math-based manufacturing strategy has been outlined earlier in this document. It is possible to execute the math-based strategy without OMAC controllers, but most likely an additional personal computer is required for each machine to off-load many functions that need to be done and cannot be done easily by a proprietary controller. Some examples of these functions are post-processing of part programs at the controller, integration of sensors for in-process gauging and closed loop control, data monitoring and analysis for statistical process control, etc.
Using a PC-based open controller removes the need of adding an additional computer for each machine and provides the capability and flexibility to fully support the math-based manufacturing requirements.
6) Leverage the technology and cost advantage of the personal computer marketplace;
Strategically, it is also essential for GMPTG to take advantage of the fast advancement of personal computer technologies to enhance the capability of control systems. Innovations in personal computer hardware and software technologies occur every few months, and in most cases, the technologies are backward compatible. Proprietary control suppliers utilize many of the same technologies in their control products. However, the availability of these control products is lagging the computer market by approximately 18-24 months. It is also important to note that implementation costs of PC-based control systems are lower because the large volume of the personal computer market drives the cost of components lower.
7) Start encouraging control vendors to 'open' up their control architecture.
Open systems foster competition. Since end users have the ability to select control components and integrate them into an open controller platform, they can select and use the best technology in a particular area and not be constrained to purchase the complete systems from a single vendor. The ability to choose will encourage the traditional control suppliers to make their products more open and modular so that they can also take advantages of technologies that are developed by other companies. This approach will allow them to offer the best 'integrated' solution.
It is to the benefit of GMPTG to have control vendors that supported GMPTG programs over the years to embrace the OMAC direction. It is never the intention of the OMAC activities to keep the traditional control suppliers out of GMPTG programs. It is intended to develop a new kind of partnership, with emphasis on implementation of the most appropriate technologies, separation of component procurement and integration support, and close working relationships, that will benefit all parties.