# Research on a PSO-H-SVM-Based Intrusion Detection Method for Industrial Robotic Arms
## 4 Experiments and Evaluation of Results
### Physical Process Logic Attack  
Nowadays, all attacks against robotic arms are mainly focused on vulnerabilities in the operating system and communication nodes. Since the operation of the robotic arm mainly relies on control data and feedback sensor data, attacks against control data and sensor data are, in some effect, equivalent to sensor failure or actuator failure in the physical domain, respectively [10]. After the control data are planned by the ROS, they are packaged as EtherCAT data packets for distribution. The data packaging junction is easily damaged by an attacker who can overwrite the normal control data with false data for data packaging and distribution. An attack on the control data can easily cause confusion in the robot operation and result in a physical domain attack, which can have serious consequences. For the intelligent operation line, each robotic arm has a predetermined execution trajectory and status to ensure the completion of the closure operation process. Physical process logic (PPL) attacks occur during the operation of the robotic arm, that is, by overwriting normal control data with control data of the wrong state, which may lead to disorder in the robotic arm operation system and produce very serious damage in the physical domain [23]. A robotic arm was built in the laboratory for the grasping and placing of objects. By controlling the robotic arm, a round of closure grasping and placing operations can be completed; that is, the robotic arm runs from the initial position to the position where the item is placed, the gripper closes for grasping and then runs to the designated position for placing, and then the gripper opens to place the item and runs to the initial position. The complete joint state data are collected during the whole operation process, and the joint angle change of the whole process is made into a two-dimensional image, as shown in Figure 6a. The horizontal coordinate \"np\" indicates the number of data points acquired, the vertical coordinate \"joint angle\" indicates the joint angle of each joint of the robot arm during operation, and the unit is the angle system. We can clearly observe each logical state of the robotic arm. Each operating state is marked in the figure, where s1 indicates running from the initial position to the position where the item is placed, s2 indicates that the gripper is closed for grasping, s3 indicates running to the specified placed position, s4 indicates that the gripper is open for placing the item, and s5 indicates running to the initial position. If the PPL attack is performed on the control data completed for planning, the attacker uses any one state of data to overwrite the normal control data before the control data are sent down during normal operation, which will lead to disorder in the logic state of the robotic arm operation. The attack model description formula is as follows:  
\[\text{Normal state transfer}:\ \text{s}_{\text{i+1}} =\text{e}_{\text{i+1}},\ \text{i}=0,1,\cdots,4 \tag{9}\] \[\text{PPL attack state transfer}:\ \ \text{s}_{\text{i+1}} =\left\{ \begin{array}{c}\text{e}_{\text{i+random}(-(\text{i-1}), \ 0)},1\leq\text{i}\leq 4\\ \text{e}_{\text{i+random}(2,\text{n-i})},0\leq\text{i}\leq 3\end{array} \right. \tag{10}\]  
where, \(\text{s}_{\text{i+1}}\) is the next transfer state in the normal state, \(\text{\ s}_{\text{i+1}}\) is the next transfer state in the attack state, \(\text{e}_{\text{i}}\) is the current running state, \(\text{e}_{\text{i+x}}\) is a post-shift states of state i in the state set, \(\text{random}(-(\text{i}-1),\ 0)\) and \(\text{random}(2,\text{n}-\text{i})\) are random integers in the range of \((-(\text{i}-1),\ 0)\) and \((2,\text{n}-\text{i})\), and n is the total number of states, which has a value of five. The attack generated as shown in Figure 6b is to run to the placement location without executing the grab action, or to run to the home location after reaching the specified placement location without executing the placement action, which can cause damage to the physical domain.