Step 1: TRIZ Analysis of the Main Problem
According to RQ1 (How can the limitations of a smart lawnmower be resolved using the TRIZ approach?), the constraints can be solved using CEC analysis, technical contradictions, physical contradictions and substance field (Su-field) analysis.
Resolving Constraint 1:
Figure 2 shows the CEC analysis for constraint 1. There are a total of 2 causes for constraint 1, namely: (a) the power or torque of the mower is insufficient, and (b) the chosen mode of locomotion is not suitable for the design. For each cause mentioned, an obvious solution is proposed. A step-by-step application of the TRIZ analysis tools for the identified constraint follows:
Constraint 1: Cannot move smoothly on uneven grassland or ground with tall grass.
- (a)
Use motors with higher power or torque.
- (b)
Use other types of locomotion.
- (c)
Centre pivot.
- (d)
Larger rear wheels.
Technical Contradiction (TC) and TRIZ Contradiction Matrix for Constraint 1: Inventive problems are written in terms of “if-then-but”. Since this constraint has 2 main causes, there are also 2 sets of technical contradictions. The parameters in both sets of technical contradictions have been identified, as shown in
Table 2.
TC1: If motors with higher power or torque are used, then the movement of the mower will be smoother (#35, adaptability), but more energy will be consumed (#19, energy spent by a moving object).
TC2: If another type of locomotion is used, then the movement of the lawnmower will be smoother (#35, adaptability), but the complexity of the design increases (#36, complexity of the device).
The inventive principles are also identified using the Altshuller or contradiction matrix, as shown in
Table 3. By intersecting the improving and worsening parameters, a list of inventive principles can be extracted from the matrix.
Table 4 shows the proposed solutions based on the inventive principles obtained from the intersection of parameters #35, adaptability, and #19, energy spent by a moving object within the contradiction matrix. The proposed solutions are based on the guidelines or rules of the inventive principles.
Table 5 shows the proposed solutions based on the inventive principles resulting from the intersection of parameters #35, adaptability and #36, complexity of the device, within the contradiction matrix.
Physical Contradiction (PC) for Constraint 1: In this study, the formulation of the physical contradictions for the two identified root causes involves two justified contradictory (opposing) requirements for one of the parameters of the technical system or its components. The ideas or solutions are proposed based on the inventive principles for separation in space and time, whichever applies. The strategy of separation in time is not applicable. Therefore, only spatial separation is considered.
PC1: The power or torque of the motor must be high to ensure smooth movement (+a), and the power or torque must be low to save energy (−a).
- i.
Space:
(+a): Where does the lawnmower need high-power and high-torque motors? (Answer: on uneven grassland.)
(−a): Where does the lawnmower need low-power, low-torque engines? (Answer: on level grassland.)
- ii.
Time:
(+a): When does the lawnmower need high-power and high-torque engines? (Answer: during operation).
(−a): When does the lawnmower need low-power, low-torque engines? (Answer: when not in use—not applicable.)
PC2: The other method of locomotion must be used to allow smooth movement (+b), and the original method of locomotion must be used to obtain a simpler design (−b).
- i.
Space:
(+b): Where does the lawnmower need the other method of locomotion? (Answer: on uneven grassland.)
(−b): Where does the lawnmower need the original kind of locomotion? (Answer: on level grassland.)
- ii.
Time:
(+b): When does the lawnmower need the other type of locomotion? (Answer: while it is in operation.)
(−b): When does the lawnmower need the original mode of locomotion? (Answer: when not in use—not applicable.)
The inventive principles used for the strategy of separation in space are listed in
Table 6. Based on the rules of these inventive principles, several proposed solutions can be outlined.
Substance Field (Su-Field) Analysis for Constraint 1: The Su-field model is constructed. The ineffective complete systems are identified, where the standard wheels do not move effectively on uneven grassland because the electric motor does not deliver enough power with the existing specifications (see
Figure 3).
The solution model underlying the incomplete Su-field model involves a change of substance or field. An improved Su-field model is constructed by adding an additional field (solar energy) between S2 and S3 (see
Figure 4). The ineffective system is solved by adding solar energy (field) to supply the electric motor with additional energy.
Resolving Constraint 2:
Figure 5 shows the CEC analysis for constraint 2. According to the CEC, the product needs to be recharged frequently because the battery runs out quickly due to its low capacity. For each stated cause, an obvious solution is proposed. A step-by-step application of the TRIZ analysis tools for the identified constraint follows:
Constraint 2: Needs frequent recharging.
- (a)
Provide holes in the body of the mower wherever possible to reduce weight.
- (b)
Use a solar charge controller.
Technical Contradiction (TC) and TRIZ Contradiction Matrix for Constraint 2: The technical contradiction follows the same if-then-but method as in the previous section. The system parameters associated with the technical contradiction are listed in
Table 7, and the inventive principles resulting from the intersection of the selected system parameters in the contradiction matrix are listed in
Table 8. The statement of the contradiction is proposed as follows:
TC: If a battery with a higher capacity (or more batteries) is used, then the lawnmower can work longer (#19, use of energy by the moving object), but the weight of the lawnmower is increased as a result (#1, weight of the moving object).
Table 9 shows the proposed solutions based on the inventive principles resulting from the intersection of parameters #19, use of energy by the moving object, and #1, weight of the moving object within the contradiction matrix.
Physical Contradiction (PC) for Constraint 2: The physical contradiction formulated for constraint 2 follows the same process as in the previous section. The ideas or solutions are proposed based on the inventive principles for separation in space, time, and conditions, whichever is applicable. The two strategies of separation in space and time are not applicable. Therefore, only the strategy of separation by conditions is considered.
PC: The capacity of the battery must be high to increase the working time (+a), and the capacity of the battery must be low to reduce product weight (−a).
- i.
Place:
(+a): Where does the lawnmower need the high-capacity battery? (Answer: on the grassland.)
(−a): Where does the lawnmower need the low-capacity battery? (Answer: not on the grassland—not applicable.)
- ii.
Time:
(+a): When does the lawnmower need the high-capacity battery? (Answer: while it is in operation.)
(−a): When does the lawnmower need the low-capacity battery? (Answer: when it is not in operation—not applicable.)
- iii.
Condition:
(+a): The lawnmower needs a higher-capacity battery when it has to work for a longer period of time.
(+a): The lawnmower requires a lower-capacity battery when it does not need to operate for a prolonged period of time.
The inventive principles used for the strategy of separation by conditions are listed in
Table 10. Based on the rules of these inventive principles, several proposed solutions can be outlined.
Substance Field (Su-Field) Analysis for Constraint 2: Similar to the previous section, a Su-field model is constructed. The ineffective overall system is identified, where the battery is not effectively charged by the electric power supply (see
Figure 6).
The improved Su-field model involves a change of substance. The ineffective system is essentially solved by adding a solar panel (substance) to the model (See
Figure 7). This allows the lawnmower to be charged while mowing under the sun, which increases the mowing time.
Resolving Constraint 3:
Figure 8 shows the CEC analysis for constraint 3. Based on the CEC, the availability of the product in the local Malaysian market is estimated to be low because the product is costly due to its expensive components or parts, which is due to the lack of new or advanced technologies in robotic mowers. Some possible solutions that are obvious to designers can be suggested as follows:
Constraint 3: Availability in the local Malaysian market is considered to be low.
- (a)
Use other materials or technologies to minimise cost.
- (b)
Use a modular design concept to reduce maintenance costs.
Technical Contradiction (TC) and TRIZ Contradiction Matrix for Constraint 3: The technical contradiction follows the same if-then-but method as in the previous section. The system parameters associated with the technical contradiction are listed in
Table 11, and the inventive principles resulting from the intersection of the selected system parameters in the contradiction matrix are listed in
Table 12. The statement of the contradiction is proposed as follows:
TC: If new or advanced technologies are used, then the lawnmower can perform better (#27, reliability), but the complexity of the lawnmower is increased (#36, device complexity).
Table 13 shows the proposed solutions based on the inventive principles resulting from the intersection of parameters #27, reliability, and #36, device complexity, within the contradiction matrix.
Physical Contradiction (PC) for Constraint 3: The physical contradiction proposed for constraint 3 follows the same procedure used in the previous section. The solutions are proposed according to the inventive principles for separation in space, time, and conditions. However, the two strategies of separation in space and time are not applicable. Therefore, the strategy of separation by conditions is considered.
PC: The technologies used must be more advanced to improve product performance (+a) and the technologies used must be less advanced to reduce product complexity (−a).
- i.
Space:
(+a): Where does the lawnmower need more advanced technologies? (Answer: on the grassland.)
(−a): Where does the lawnmower need less advanced technologies? (Answer: not on the grassland—not applicable.)
- ii.
Time:
(+a): When does the lawnmower need more advanced technologies? (Answer: while it is in operation.)
(−a): When does the lawnmower need less advanced technologies? (Answer: when it is not in operation—not applicable.)
- iii.
Condition:
(+a): The lawnmower needs more advanced technologies if it is to perform better.
(−a): The lawnmower needs less advanced technologies if it is to reduce design complexity.
The inventive principles normally used to support the strategy of separation by conditions have already been listed in
Table 10. However, the researcher was not able to propose a solution or idea based on any of the principles. Therefore, this tool was eventually not used in resolving constraint 3.
Substance Field (Su-Field) Modelling for Constraint 3: Similar to the previous section, a Su-field model is created. The excessive complete system is identified, where the sophisticated system excessively controls the smart lawnmower (see
Figure 9).
The improved Su-field model involves a change of substance. The excessive complete system is basically solved by replacing the advanced system with one that is simple but sufficient to perform the specific tasks of a smart lawnmower (see
Figure 10).