**6. Discussion**

**Group Success rate (%) Reason for failure and test number**

**Group Success rate (%) Reason for failure and test number**

11 15

8 11

4

*β* 75 2

*α* 85 3

*Industrial Robotics - New Paradigms*

*β* 85 1

*γ* 90 3

*α* 75 1

*β* 80 —

**Table 2.**

**Table 1.**

**Table 3.**

**Table 4.**

**96**

*α* 100 — ———

*γ* 100 — ———

**Group Success rate (%) Reason for failure and test number**

— — — —

— — —

*γ* 100 — ———

*α* (8) 50 12.5 37.5 0 *β* (12) 58.33 25 16.67 0 *γ* (2) 100 0 0 0 Three groups 59.09 18.18 22.73 0

*Success rate for step climbing (0.4 km/h), reason for failure, and test number.*

*Success rate for step climbing (0.3 km/h), reason for failure, and test number.*

*Success rate for step climbing (0.5 km/h), reason for failure, and test number.*

*Ratio of reason for failure of the robots to climb the step (0.3–0.5 km/h).*

**Group (total number of failures) Ratio of reason for failure**

**[Col. AS] [Tip.A] [Col.BS] [Tip.B]**

**[Col. AS] [Tip.A] [Col.BS] [Tip.B]**

— — —

— — —

— —

— — —

— — —

— —

**[Col. AS] [Tip.A] [Col.BS] [Tip.B]**

**[Col. AS] (%) [Tip.A] (%) [Col.BS] (%) [Tip.B]**

— 2 — — —

— — — 11 —

— — 4 7 8

14 — — — — — — — —

— — —

— — —

— —

— — — — —

— — — —

— — — — —

> In this section, we discuss the remote operability of the proposed system based on the results of experiments.

### **6.1 Correlation between the robot velocity and the success rate**

**Figure 17(a)** shows the correlation between the robot velocity and the success rate for step climbing for the three experiments by group (**Tables 1**–**3**). The success rate for group *γ* was high as a whole and increased to 100% at 0.4 and 0.5 km/h. In contrast, the success rate for group *α* increased at 0.4 km/h but decreased at 0.5 km/h. The success rate for group *β* decreased at 0.4 km/h and increased at 0.5 km/h. Therefore, the trends in the experimental results are not consistent.

**Figure 17(b)** shows the total success rate at 0.3–0.5 km/h for the three groups (**Tables 1**–**3**). The results of the experiments were different from what we had expected, and the remote operability of the step climbing system did not depend on

**Figure 17.** *Ratio of successful step climbing: (a) success rate for each group and (b) total success rate for the three groups.*

the velocity of the robots. If the velocity is sufficiently higher than 0.5 km/h, the success rate is likely to be reduced. The operators had to manipulate the robots hurriedly in the experiment in which the velocity was 0.5 km/h. However, the step climbing method was based on the premise that the robots move slowly and in balance with each other and using fast robots is beyond the scope of the proposed method.

they intended to do next. As such, conversation was judged to make up for the lack

**Group Total success rate for step climbing (%)**

*Cooperative Step Climbing Using Connected Wheeled Robots and Evaluation of Remote…*

86.67 80 96.67

after the second experiment (*vA* ¼ 0.4 km/h) because they felt that they were skillful operators and were able to manipulate the robots without conversation. In addition, these subjects were tired from repeating the experiments. The subjects of

Based on the results of the experiments, it is clear that the cooperative step climbing method can be performed using teleoperated robots. However, it seems reasonable to assume that the ability of the robot system was greatly influenced by loss of concentration and conversation between the robot operators. Even if the operators had sufficient skill to manipulate the robot, they sometimes became tired, and did not converse. The construction of an assist system for manipulation should

The present paper described cooperative step climbing using two wheeled robots connected by a passive link. We constructed a teleoperated robot system and car-

1.The cooperative step climbing method is practical even if the robots are

2.A theoretical analysis and the results of simulations clarified the correlations among the manipulation time for the robot, the velocity of the robot, and the

3.The ability of operators who reached sufficient proficiency in teleoperating the

4. It was difficult to perform teleoperation using only moving images from the cameras on the robots because the operators were not able to recognize the

between the front wheels and the step. If the robots have an assistance system that can detect the distance between the robot and a step, the capabilities of

6.Loss of concentration by the operators greatly influenced the operation. Even if the operators had sufficient skill to manipulate the robot, when they became

5.Approximately 82% of the step climbing failures were due to collisions

group *β* (*s*<sup>3</sup> and *s*4) had few conversations throughout the experiments.

In contrast, the subjects of group *α* (*s*<sup>1</sup> and *s*2) conversed little with their partners

of information during teleoperating the robots.

*DOI: http://dx.doi.org/10.5772/intechopen.90162*

*Total success rate for step climbing for each group (0.3–0.5 km/h).*

**6.5 Results of the experiments**

improve the step climbing ability.

controlled by teleoperation.

ried out experiments. Our conclusions are as follows:

height of the front wheels in climbing a step.

robots does not depend on the velocity of the robots.

overall status of the robots during step climbing.

such teleoperated robots should improve greatly.

**7. Conclusion**

**99**

*α β γ*

**Table 5.**

### **6.2 Teleoperation skill**

As mentioned above, all subjects knew the step climbing procedure before the experiments and became sufficiently proficient at teleoperating the robots. The experiments were carried out at velocities of 0.3, 0.4, and 0.5 km/h, and 20 tests were performed for each velocity. Thus, each subject performed a total of 60 tests. **Tables 1**–**3** show that the failures in the experiments by the three groups occurred not only in the early stages of each experiment (1st–7th test) but also in the final stages (14th–20th test). If the subjects did not have sufficient skill to operate the robots, failures should frequently have occurred in the early stages of the experiments at 0.3 km/h. The skill of the operators would be expected to improve as the tests progressed, thus reducing the failure rate in the later tests at each velocity. Also, if the subjects did not have enough skill to react to the speed of the robot, failures should frequently have occurred in the early stages of each experiment (1st– 7th test). However, from the results (**Tables 1**–**3**), failures also occurred in the final stages (14th–20th test), and the success rate was not improved except for group γ (**Figure 17(a)**). Thus, as far as these experiments are concerned, it is clear that the reason for failure was not lack of operator skill.

### **6.3 Lack of information during teleoperation**

Based on interviews with subjects after the experiments, one reason for failure was a lack of information while teleoperating the robots. In these experiments, each robot had one camera on its body, and each subject teleoperated a robot while viewing moving images. The inclines of the robot cameras were set such that the subjects were always able to view the moving images of *Robot A* or the step (**Figure 7(a)** and **(b)**). The subjects had to piece together the status of the climbing robots based on information from the moving images.

We conducted an additional experiment in which a fixed external camera was installed that could view both robots at the same time (see Appendix B, **Figures B1** and **B2**). This experiment was performed using only a single group. However, based on the results, we are fairly certain that using an external camera is effective for teleoperation.

### **6.4 Losing concentration during teleoperation and conversation between operators**

**Table 5** lists the total success rate for step climbing for each group (0.3–0.5 km/h). The results for group *γ* were the best (96.67%), and the results for group *β* were the worst (80%). There is a difference of approximately 17% for the total success rate between groups *γ* and *β*, which is not small.

In the experiment in which the velocity of the robots was 0.5 km/h, the operators had to teleoperate the robots hurriedly, and as a whole did not have enough time to converse while manipulating the robots.

The subjects in group *γ* (*s*<sup>5</sup> and *s*6) were continuously conversing with each other throughout the experiments and frequently talked about their actions and what

*Cooperative Step Climbing Using Connected Wheeled Robots and Evaluation of Remote… DOI: http://dx.doi.org/10.5772/intechopen.90162*


**Table 5.**

the velocity of the robots. If the velocity is sufficiently higher than 0.5 km/h, the success rate is likely to be reduced. The operators had to manipulate the robots hurriedly in the experiment in which the velocity was 0.5 km/h. However, the step climbing method was based on the premise that the robots move slowly and in balance with each other and using fast robots is beyond the scope of the proposed

As mentioned above, all subjects knew the step climbing procedure before the experiments and became sufficiently proficient at teleoperating the robots. The experiments were carried out at velocities of 0.3, 0.4, and 0.5 km/h, and 20 tests were performed for each velocity. Thus, each subject performed a total of 60 tests. **Tables 1**–**3** show that the failures in the experiments by the three groups occurred not only in the early stages of each experiment (1st–7th test) but also in the final stages (14th–20th test). If the subjects did not have sufficient skill to operate the robots, failures should frequently have occurred in the early stages of the experiments at 0.3 km/h. The skill of the operators would be expected to improve as the tests progressed, thus reducing the failure rate in the later tests at each velocity. Also, if the subjects did not have enough skill to react to the speed of the robot, failures should frequently have occurred in the early stages of each experiment (1st– 7th test). However, from the results (**Tables 1**–**3**), failures also occurred in the final stages (14th–20th test), and the success rate was not improved except for group γ (**Figure 17(a)**). Thus, as far as these experiments are concerned, it is clear that the

Based on interviews with subjects after the experiments, one reason for failure was a lack of information while teleoperating the robots. In these experiments, each robot had one camera on its body, and each subject teleoperated a robot while viewing moving images. The inclines of the robot cameras were set such that the subjects were always able to view the moving images of *Robot A* or the step

(**Figure 7(a)** and **(b)**). The subjects had to piece together the status of the climbing

We conducted an additional experiment in which a fixed external camera was installed that could view both robots at the same time (see Appendix B, **Figures B1** and **B2**). This experiment was performed using only a single group. However, based on the results, we are fairly certain that using an external camera is effective for

**Table 5** lists the total success rate for step climbing for each group (0.3–0.5 km/h). The results for group *γ* were the best (96.67%), and the results for group *β* were the worst (80%). There is a difference of approximately 17% for the total success rate

In the experiment in which the velocity of the robots was 0.5 km/h, the operators had to teleoperate the robots hurriedly, and as a whole did not have enough

The subjects in group *γ* (*s*<sup>5</sup> and *s*6) were continuously conversing with each other throughout the experiments and frequently talked about their actions and what

method.

teleoperation.

**98**

**between operators**

between groups *γ* and *β*, which is not small.

time to converse while manipulating the robots.

**6.2 Teleoperation skill**

*Industrial Robotics - New Paradigms*

reason for failure was not lack of operator skill.

**6.3 Lack of information during teleoperation**

robots based on information from the moving images.

**6.4 Losing concentration during teleoperation and conversation**

*Total success rate for step climbing for each group (0.3–0.5 km/h).*

they intended to do next. As such, conversation was judged to make up for the lack of information during teleoperating the robots.

In contrast, the subjects of group *α* (*s*<sup>1</sup> and *s*2) conversed little with their partners after the second experiment (*vA* ¼ 0.4 km/h) because they felt that they were skillful operators and were able to manipulate the robots without conversation. In addition, these subjects were tired from repeating the experiments. The subjects of group *β* (*s*<sup>3</sup> and *s*4) had few conversations throughout the experiments.

### **6.5 Results of the experiments**

Based on the results of the experiments, it is clear that the cooperative step climbing method can be performed using teleoperated robots. However, it seems reasonable to assume that the ability of the robot system was greatly influenced by loss of concentration and conversation between the robot operators. Even if the operators had sufficient skill to manipulate the robot, they sometimes became tired, and did not converse. The construction of an assist system for manipulation should improve the step climbing ability.

## **7. Conclusion**

The present paper described cooperative step climbing using two wheeled robots connected by a passive link. We constructed a teleoperated robot system and carried out experiments. Our conclusions are as follows:


tired, the success rate for step climbing decreased. The robots are connected by a link and are affected by the force exerted by each other. Therefore, when one or both operators lose concentration, the robots are not able to ascend the step.

**Appendix B**

*DOI: http://dx.doi.org/10.5772/intechopen.90162*

teleoperation.

**Figure B1.**

**Figure B2.**

**Table B1.**

**101**

*the robots using the external camera.*

Group *α* conducted 20 tests (maximum velocity 0.3 km/h). **Table B1** lists the experimental results. It can be seen that the success rate was improved from 85 (**Table 1**) to 95%. Based on interviews with subjects *s*<sup>1</sup> and *s*<sup>2</sup> (operators in group *α*), teleoperation in this manner was easier than using cameras on the robots. Although the experimental results were obtained using only one group, we are fairly certain that using an external camera is effective for teleoperation. If the environment does not allow for the placement of an external camera, the robots should have a sensor

*Cooperative Step Climbing Using Connected Wheeled Robots and Evaluation of Remote…*

system that can show the status of the robots and the step for assistance in

*A schematic of the setup used in an experiment in which an external camera (iBuffalo BSW3KMW01,*

*The robots did not have a camera on their body in this case, but the operators were able to determine the status of*

*α* 95% 18th ———

**[Col. AS] [Tip.A] [Col.BS] [Tip.B]**

**Group Success rate Reason for failure and test number**

*Ratio of reason for failure of the robots to climb the step (0.3–0.5 km/h).*

*maximum frame rate: 30 fps) was used to view both the robots and the step together.*

7. It is reasonable to assume that conversation between the operators made up for lack of information during teleoperation.

In the future, we intend to construct an augmented reality system to improve remote operability and to perform experiments to confirm its validity. In addition, we will construct an autonomous robot that has sensors and stereo cameras.
