We show that the chemical structures of silicone oils can have an important role in the giant electrorheological (GER) effect. The interaction between silicone oils and solid nanoparticles is found to significantly influence the ER effect. By increasing the kinematic viscosity of silicone oils, which is a function of siloxane chain length, sol-like, gel-like and clay-like appearances of the constituted ER fluids were observed. Different functional-group-terminated silicone oils were also employed as the dispersing media. Significant differences of yield stress were found. We systematically study the effect of siloxane chain lengths on the permeability of oils traveling through the porous spaces between the particles (using the Washburn method), oils adsorbed on the particles' surface (using FT-IR spectra), as well as their particle size distribution (using dynamic light scattering). Our results indicate the hydrogen bonds are instrumental in linking the silicone oil to GER solid particles, and long chain lengths can enhance the agglomeration of the GER nanoparticles to form large clusters. An optimal oil structure, with hydroxyl-terminated silicone oil and a suitable viscosity, was chosen which can create the highest yield stress of ∼300 kPa under a 5 kV mm(-1) DC electric field.

Parameters of theodolite measuring motor will vary with duty conditions bringing about aiming control system chaotic, which is harmful for the aiming system and the aiming result. In order to be close to reality, considering that the aiming system is under time-varying load and inside disturbances, the dynamic model was established and analyzed. The existence of chaos was proved. Due to terminal sliding control with good robustness, fast dynamic response, finite time convergence and high tracking precision, PI terminal sliding structure and control strategy were given, and the system stability was analyzed. The chaotic orbits of aiming motor system were stabilized to arbitrary chosen fixed points and periodic orbits by means of sliding mode method. Simulation results show that PI terminal sliding mode control can realize the stability and accuracy of aiming motor control system, and overcome the negative influence of the chaos for the aiming system.