# Electromagnetic Switching Multiple Grasping Modes Robot Hand
## 2 Design Concept of the ESMGM Hand
### Integration of Multiple Grasping Modes  
To realize grasping mode fusion, we need to choose the appropriate method to combine them according to the characteristics of the three grasping modes. Common methods include direct series fusion and parallel switchable fusion. As shown in Figure 1, the parallel grasping mode and coupled grasping mode always happen at the beginning stage of the entire grasping motion, but they put forward totally different requirements for the motion characteristic of the distal phalange and distal joint axis. Under parallel grasping mode, the distal phalange should keep parallel to the initial state. On the contrary, under the coupled grasping mode, the distal phalange should rotate coupled with the proximal phalange by a fixed ratio. Therefore, these two grasping modes, which should be arranged at the same stage, are mutually exclusive. In the above case, to effectively realize grasping mode integration, a switchable fusion method is proposed in the ESMGM robot finger. The operator can choose to execute with the parallel grasping mode or the coupled grasping mode for the first stage of the grasping motion, the switching of the two modes is realized by switching devices. The self-adaptive grasping mode requires that all phalanges completely envelop the object, so it is often arranged as the final stage of the grasping motion and forms a good connection with the parallel grasping mode or coupled grasping mode. Therefore, after the proximal phalange contacts the object, the first stage of grasping motion will be finished, and the ESMGM robot finger will enter the self-adaptive grasping mode; namely, the successful transformation from both parallel grasping mode and coupled grasping mode to self-adaptive grasping mode should be guaranteed with specific mechanism design. Above all, the parallel grasping mode and coupled grasping mode are integrated with a shunt connection method, and they are in series with the self-adaptive grasping mode. To realize the fusion function mentioned above, a switchable fusion mechanism of coupled, parallel grasping, and self-adaptive grasping (switchable CPS mechanism) is proposed. It contains a motor, two-way gear sets, and a switching device, and it overcomes the certain incompatibility between parallel pinching and coupled enveloping; therefore, it is the foundation of the ESMGM hand and endows it with versatility. Figure 2 shows the working principle diagram of the switchable CPS mechanism. The motor is fixed on the base and provides the torque, turning the proximal phalange. The two transmission gear trains, namely the parallel grasp gear train and coupled gear train, are arranged inside the proximal phalange. The lower ends of the two gear trains are connected with the switching device, which is arranged on the base, and the upper output end is fixedly connected with the distal phalange. According to the switching state of the switching device, the whole switchable CPS mechanism has two working modes, namely parallel grasping mode and coupled grasping mode. Figure 1: Integration method of parallel grasping mode, coupled grasping mode, and self-adaptive grasping mode. Parallel grasping mode  
When the switching device is switched to the left, the whole switchable CPS mechanism will be under parallel grasping mode. The parallel grasp gear train is working. The switching device connects with the parallel grasp gear train; thus, it will be tensioned with the elastic element. Meanwhile, the coupled gear train is released and under a follow-up state. After the motor starts, it drives the proximal phalange and rotates around the first joint axis. When focusing on the motion transmission of the parallel grasp gear train, the proximal phalange could be considered as the base.