By Xiaoming Mao, Xueqing Zhang and Simaan AbouRizk
Su-field analysis, one of the major contributions of TRIZ, is a useful tool for identifying problems in a technical system and finding innovative solutions to these identified problems. However, the 76 standard solutions of su-field analysis make the implementation of this tool difficult as they contain repetitive information from other TRIZ tools, give special favors in utilizing certain fields and can not be fully explained using the su-field model. Consequently, users may feel frustrated and often give up. To help users carry out su-field analysis and find the right problem-solving solutions in an easy manner, this paper summarizes/condenses the 76 standard solutions into seven general principles with graphic demonstrations and examples. The seven generalized standard solutions can be deployed to fix su-field models for all types of relationships between substance S1 and S2.
Su-field analysis is a basic concept used to symbolize a technical system and identify its completeness and effectiveness. Recognized as one of the most valuable contributions of TRIZ, su-field analysis is able to not only model a system in a simple graphical approach and identify problems, but also offer standard solutions to improve the system.
According to TRIZ, the rationale of creating a su-field model is that a system, with the ultimate objective to achieve a function, normally consists of two substances and a field. The term S1 is used to represent an object that needs to be manipulated. The term S2 is a tool to act upon S1. Both substances can be as simple as a single element or as complicated as a big system with many components, which can also be explained by individual su-field models. The field is the needed energy to enable the interaction between the substances. The states of substances can be typical physical forms (e.g., gas, liquid and solid), interim or composite forms (e.g., aerosol, power, porous).  Likewise, the field can refer to a broad range of energy, including mechanism, chemistry, physics, acoustics, optics and radiations.
Genrich Altshuller and his colleagues, the creators of TRIZ, graphically represent a su-field model as a triangle. This is a simple and ingenious way to explain a technical system. Assuming that the field is generated by a hidden substance, the triangle can be simplified into a dumbbell shape with the field indicated on top of the arrow and the relationship indicated underneath the arrow, as shown in Figure 1. There are mainly five types of relationship among the substances: useful impact, harmful impact, excessive impact, insufficient impact and transformation.  Among them, useful and harmful interactions are the most common relationships.
The su-field model is a fast and simple analytic tool to identify problems in a system and provide insights toward the evolution of this system. Once a model is created, su-field analysis can first tell if any of the three elements of the model is missing or if there are undesired effects in the system. Then, it points out the direction for the improvement of the system. A complex system can be modeled using multiple connected su-field models. In general, there are four types of basic su-field models: 1) an effective complete system, 2) an incomplete system that requires completion or a new system, 3) a complete system that requires improvement to create or enhance certain useful impact and 4) a complete system that requires the elimination of some harmful or excessive impact. 
Once a technical system is simplified into a su-field model, its potential problems can be identified through analyzing undesired interactions resulted from the model. Problematic su-field models may be fixed by exploring the underlying ideas that generated previous patents. Based on their intensive research of a huge number of patents, Genrich Altshuller and his colleagues identified 76 standard solutions to fixing problematic su-field models. These 76 solutions may be categorized into five classes:
Class 1: Construct or destroy a su-field (13 standard solutions)
Class 2: Develop a su-field (23 standard solutions)
Class 3: Transition from a base system to a super-system or to a subsystem (6 standard solutions)
Class 4: Measure or detect anything within a technical system (17 standard solutions)
Class 5: Introduce substances or fields into a technical system (17 standard solutions) 
Although su-field analysis provides a simple means to model systems and reveal their problems, the more than 70 standard solutions may make users rather confused and overwhelmed in their searching for answers from these many possible solutions.
After careful evaluation of the 76 standard solutions, it is recommended that these standard solutions be significantly reduced to avoid excessive redundancy and details. In addition, the standard solutions should be depicted as general principles that are not field-specific. For those solutions provided within a certain field to improve the su-field model, they need to be removed from the standard solutions and added into other TRIZ tools where they are suitable. The standard solutions should be able to improve all types of problematic su-field models, be it incomplete or with harmful, insufficient or excessive impact. As a result, the 76 solutions have been condensed and generalized into seven standard solutions. These seven generalized standard solutions are discussed in following with graphic demonstrations and examples. Please note although these generalized solutions are discussed in the context of a su-field model with harmful impact, they are applicable to su-field models with other types of problems, for example, excessive and insufficient interactions between substances.
Complete a su-field model if any of its three components is missing, as shown in Figure 2.
Example: Having only a truck cannot move dirt. Three components: materials for handling, truck and mechanical force (produced from loader), are required to conduct the loading process.
The physical and/or chemical characteristics of substance S2 may be changed internally or externally and temporarily or permanently in order to eliminate or reduce harmful impact, as shown in Figure 3. Modification can mean changing substance S2 into another form, material or system as long as the su-field system with which S2 is associated carries out the same useful function. Additives may need to be added to the system in this modification.
Example: A rubber hammer is used to curve a metal sheet instead of a regular hammer with a steel head, which could cause damage. A screwdriver is magnetized so that it can easily guide the screw to its position.
The physical and/or chemical characteristics of substance S1 may be altered internally or externally, so that it becomes less sensitive or insensitive to a harmful impact, as seen in Figure 4. The modification may be either temporary or permanent. Additives may be needed in this modification.
Example: Tunneling through sandy soil is costly and has a high possibility of causing soil collapse. One method to overcome this problem is to freeze soil prior to tunneling.
Changing the existing field while keeping the same substances may be a choice to reduce or removing the harmful impact, as shown in Figure 5. Changing the existing field means increasing, decreasing the existing field, or completely removing the existing field and using another one.
Example: During winter construction, cold temperatures deteriorate construction productivity. As a counter-measure, the working area is enclosed with a heating system to increase the environmental temperature to an appropriate degree.
In a system in which harmful impact exists and substances S1 and S2 have to coexist, a counteractive field of FX may be introduced to remove, neutralize or isolate the harmful impact as shown in Figure 6. Neither S2 nor S1 will change its physical and chemical characteristics in this solution. A third substance will be introduced to provide field FX.
Example: Warm air temperature can reduce concrete curing time but raise the possibility of concrete cracking. Covering concrete with waterproof curing paper holds moisture and avoids thermal crack.
Another field may be added to work with the current field in order to increase the useful effect and reduce the negative effect of the existing system while keeping all substances intact, as shown in Figure 7.
Example: Metal parts are placed in a bath of nickel salt for plating. To increase the productivity of the process, the bath is heated to a certain temperature.
The existing su-field model can be expanded to a chain by introducing a new substance S3 to the system, as seen in Figure 8. Instead of directly acting upon S1, S2 will interact indirectly with S1 via another medium, substance S3.
Example: Direct communication between a project engineer and laborers can lead to misunderstanding and confusion. One better option is to pass the engineer's plan to site workers through the superintendent.
Tables 1 and 2 indicate the relationship between the 76 standard solutions and the seven generalized solutions. Solution 5.1.1 could be decomposed into 9 sub-solutions. Therefore, there are 84 standard solutions in total. 
Through careful examination and comparison, 40 conversional solutions are linked to the seven general solutions. This re-organization of the 76 standard solutions should make it easier to teach, and learn, su-field modeling and problem solving.
31 out of the 84 solutions are identified as the implementation of existing inventive principles, including such principles as 1 – segmentation, 3 – local quality, 4 – asymmetry, 5 – merging, 15 – dynamism, 16 – partial or excessive actions, 18 – mechanical vibration, 19 – periodic action, 20 – continuity of useful action, 23 – feedback, 26 – copying, 28 – mechanics substitution, 29 – pneumatics and hydraulics, 34 – discarding and recovering, 35 – change parameters, 36 – phase transitions and 38 – strong oxidants. 
Another six solutions, including 3.1.5 (system transition: opposite features of the whole and parts), 18.104.22.168 (use an external additive instead of an internal one), 22.214.171.124 (obtain the required additive by decomposition of either the environment or the object itself), 5.2.2 (use fields that present in the environment), 5.2.3 (use substances that are the sources of fields) and 5.4.2 (strengthening the output field when there is a weak input field), are recommended by the authors' experiences to be considered as new inventive principles since they can not be explained using the su-field model but have the nature of inventive principles.
In addition, there are seven solutions are originated from the patterns of evolution, including 2 (increase ideality), 4 (match and mismatch), 5 (increase complexity, then follow with simplicity through integration), 6 (transform from macro-system to micro-system) and 7 (increase dynamism and controllability).
Su-field analysis is a useful tool in identifying problems in a technical system and finding solutions to these problems for the improvement of the system. Nonetheless, the 76 standard solutions seem to have some shortcomings. First, users may be confused with so many possible solutions and not know which to start with. Second, the basic idea of many of these standard solutions has been repetitive in other concepts of TRIZ. Third, it may be not necessary to provide special attentions to certain fields. Fourth, many solutions cannot be symbolized as a su-field model. To avoid these shortcomings, the authors have examined the 76 standard solutions in detail and developed seven general solutions, removing repetitions. Those standard solutions that cannot be symbolized as a su-field model are suggested for inclusion in other parts of TRIZ to which they are suitable. These efforts enhance the logic of TRIZ in general and facilitate the application of the su-field concept in particular with improved efficiency.
Xiaoming (Robin) Mao, has been studying and conducting TRIZ-related researches for more than five years. He is currently working for Cosyn Technology as a project control specialist while finishing his Ph.D. study as a part-time student. His research interests focus on value engineering improvement, construction simulation and lean construction. The focus of his thesis is to enhance value engineering by integrating the creativity power of TRIZ. Contact Xiaoming Mao at xmao (at) telus.net.
Xueqing (Eric) Zhang is an assistant professor in the Department of Civil Engineering at The Hong Kong University of Science and Technology. He has presented papers at many international conferences and published widely in top international journals in the subject areas of construction engineering and management, project financing, and infrastructure development and management.
Simaan AbouRizk is a professor in the construction engineering and management group at the University of Alberta in Edmonton, Alberta, Canada.