**7. Conclusion**

chosen because, like the animal, the robot pulls its heavy body on the obstacle with the help of sharp elements in its feet. Unlike perhaps all known animals, Big Foot

By increasing the width of the feet and the area of the round base the robot can

Over 100 experiments for overcoming a higher obstacle were conducted. The same prototype was used, where only the feet {4} and the round base {1} were replaced. They were 3D printed and had different shapes. Two materials were used: PLA (Polylactic acid - most popular for 3D printing) and the flexible FIlaFLEX. The highest obstacle of 43 [mm] which was overcome can be seen here: Video 6; A detailed description of the results is available in [21]. After adding a "tail" to improve the balance of Big Foot, the maximum height was increased to 52 [mm]:

Experiments to overcome an obstacle with a maximum height are made with various mobile robots. Based on literary sources, [21, 23] their respective *Kro-*

Using information from the literature, the coefficient Kro can be determined for different mobile robots in **Table 1**. From the considered examples, it is seen that the highest value Kro = 0.41 is associated with the Transformable-wheeled leg robot [21]. The Big Foot robot proposed in the present study has higher values of the Kro index compared to the mobile robot [20] and the humanoid robot NAO. It can be noted that Big Foot manages to overcome this height by using only one of its two

Video 7; which corresponds to a coefficient *Kro =* 0.41, see formula 8.

can rotate its base and arms more than 360 degrees.

*3D printed feet with a complex shape, inspired by nature.*

*Collaborative and Humanoid Robots*

**Figure 11.**

walk on soft terrain (sand, snow, marsh) more easily.

indexes are defined and given in **Table 1**.

**Robot Height**

4.Transformable-wheeled

5. Micro rover – Spacecat

*Kro indices of different mobile robots.*

leg robot

[23]

**Table 1.**

**106**

motors, while all other robots use several motors.

**[mm]**

**Length [mm]**

1. MSRox 290 830 100 0.20 2 2. NAO 640 160 70 0.22 25 3. Big Foot 88 182 52 0.41 2

**Maximum height of the obstacle [mm]**

180 390 120 0.45 3

200 200 100 0.5 8

*Кro* **index** **Number of motors**

An original design of a 3D printed walking robot based on minimalistic approach is presented. This idea is intended to inspire the design of useful robot structures in the future.

It is considered a design principle and determination of the proportions of the links, based on minimizing the energy during walking.

The kinematics of the robot are analyzed and the key stages for walking on flat terrain and climbing obstacles are given.

The principles of movement are considered and the robot's ability to adapt to obstacles due to the mechanical structure is highlighted. An algorithm is shown for calculating the change in the instantaneous velocity center of one link while the robot is adapting. This is a practical example of applying kinematic methods in robotics.

The main dependences for determining the torque loading of the motor when walking are given. The results of a study of the static conditions for overcoming an obstacle and experiments with a 3D printed model are discussed. Detailed studies and simulations are given in [20, 21]. 3D printing gives new opportunities to create unconventional structures, which can change the way robots are designed.

The results of experiments with different materials and shapes for the feet and the base of the robot are discussed. Thus is detected the maximum height of the obstacle that can be overcome. After additional design changes, this height is increased to 52 [mm]. An index *Kro* is proposed which relates the robot's dimensions with the height of the obstacle it can overcome.

The results for overcoming an obstacle by different types of robots are ranked using the proposed index.

It is not easy to give definitive answers to the questions posed in the introduction. However, from the analysis of the literature and the results of this study it can be noted that:

If the number of degrees of freedom is less than two, the walking robot cannot be controlled to bypass obstacles. The idea proposed in [8] is debatable whether it can be characterized by one degree of freedom as it also uses controllable couplings. In addition, it is possible to realize the movements only sequentially.

The presented 3D printed model shows that it is possible to overcome obstacles by using a simple control system without sensors and feedback.

3D printing technology facilitates the creation of prototypes of the developed robots. It allows easy realization of links with complex shapes and connections between them.
