## 1 Introduction  
During agricultural production, soil tillage is the most key step and affects various aspects from plowing to harvest. The mechanization of agricultural tillage has allowed farmers to shake off the heavy manual plowing and planting works, which largely improve the crop production efficiency. So far, soil mechanized tillage is faced with many problems, especially the excessively large penetration resistance and large energy consumption of mechanical parts. Among all soil tillage process, the penetration process is the first step, and the most force-consuming process. Due to the rapid increase of energy-consuming, the force reduction is the most important research which need to be further researched [1]. Many studies have been conducted regarding the analysis of force during soil penetration. [PERSON] [2] reviewed the soil-machine interaction in soil bin test facilities, which are useful for the design and performance evaluation for tillage tools. [PERSON] and [PERSON] [3] evaluated the soil performance of gear couplers through a series of experiments. [PERSON] and [PERSON] [4] predicted the design requirements of common tillage tools under any field conditions, according to the design requirements of tillage tools and soil properties under given soil conditions. [PERSON] et al. [5] studied that both the soil and tool parameters influence the penetrating forces. [PERSON] et al. [6] believed that the change of soil failure modes was the major factor of soil tool design. Based on previous researches, it was proved that the force was closely related to the soil properties and tool geometry. However, the optimization method to reduce the force has not been treated in much details, which is still a research hotspot. Recently, bionic design has been regarded as a novel design method for the optimization of industries, such as the surface modification [7], bionic robots [8], and engine industries [9]. Meanwhile, the bionic design is also utilized for agricultural industries, for example, [PERSON] [10] revealed the drag reduction mechanism in fluid medium. The excavating functions of mole claws offered good clues for designing anti-resistance force soil cutting instruments and excavation instruments [11]. [PERSON] [12] analyzed the excellent property of bear claws for the future design of subsoiling tools, and found the best performance of the claw was at the rake angle of 30\({}^{\circ}\) with consideration into draft force and soil disturbance. Of all the biological characteristics, the animal teeth have the best comparability with the penetrating process, regardless of the profiles and occluding modes [13]. The animal teeth normally have four forms: Incisor (cutting and biting), canine (piercing and tearing), premolar (chopping), and molar (squashing and chewing) [13]. Badgers have sharp teeth that can easily bite wires. Our previous study showed that the badger teeth have outstanding cutting and biting capabilities due to the special surface curves and high sharpness, and thus the teeth could penetrate materials with a lower force [14]. This extraordinary phenomenon is attributed to the occlusion modes and teeth outlines of badgers [15]. On basis of research on the biological characteristics of badger teeth, our project is aimed to explore bionic design theories and techniques for tillage. Thus, the excellent curves of badger teeth can be potentially selected as the bionic prototype to optimize the soil penetration process. In this work, to optimize the penetration process and reduce the resistance, six different specimens were designed and fabricated based on the badger canine using bionic design method. Experimental investigation and numerical analysis of the penetration process for the cones with different curves were conducted to characterize and compare the penetration forces. At the same time the change of soil properties after penetration using different cones was compared. Moreover, the internal friction angle and cohesion of the soils were tested before and after experiments.