A control program to manipulate a computer to simulate behaviors of a virtual mechanism and to control synchronized driving of a plurality of servomotors by a driving unit of a mechanical testing device based on results of the simulation, the virtual mechanism comprising:- a first drive module driven according to a first driving waveform; a main shaft module connected to and driven by the first drive module; a plurality of power transmission subsystems, each of which is connected to the main shaft module and is associated with one of the plurality of servomotors respectively, wherein each of the power transmission subsystems comprises:- a second drive module (180A, 180B) driven to rotate in the same phase according to a common driving pulse; and a differential gear module comprising:- a main input shaft (151A, 151B) connected with the main shaft module to be driven according to the first driving waveform, an auxiliary input shaft (152A, 152B) connectable with the second drive module via a clutch module (170A, 170B) and capable, when disconnected, of rotating at the same phase as the first driving waveform or capable, when connected, of rotating according to said common driving pulse for providing a phase difference with respect to the first driving waveform, and an output shaft (153A, 153B) connected with an input of an output module (190A, 190B) which is associated with the respective servomotor, whereby the associated servomotor is driven by a driving waveform according to a simulated result of the input of the output module. a first drive module driven according to a first driving waveform; a main shaft module connected to and driven by the first drive module; a plurality of power transmission subsystems, each of which is connected to the main shaft module and is associated with one of the plurality of servomotors respectively, wherein each of the power transmission subsystems comprises:- a second drive module (180A, 180B) driven to rotate in the same phase according to a common driving pulse; and a differential gear module comprising:- a main input shaft (151A, 151B) connected with the main shaft module to be driven according to the first driving waveform, an auxiliary input shaft (152A, 152B) connectable with the second drive module via a clutch module (170A, 170B) and capable, when disconnected, of rotating at the same phase as the first driving waveform or capable, when connected, of rotating according to said common driving pulse for providing a phase difference with respect to the first driving waveform, and an output shaft (153A, 153B) connected with an input of an output module (190A, 190B) which is associated with the respective servomotor, whereby the associated servomotor is driven by a driving waveform according to a simulated result of the input of the output module. a second drive module (180A, 180B) driven to rotate in the same phase according to a common driving pulse; and a differential gear module comprising:- a main input shaft (151A, 151B) connected with the main shaft module to be driven according to the first driving waveform, an auxiliary input shaft (152A, 152B) connectable with the second drive module via a clutch module (170A, 170B) and capable, when disconnected, of rotating at the same phase as the first driving waveform or capable, when connected, of rotating according to said common driving pulse for providing a phase difference with respect to the first driving waveform, and an output shaft (153A, 153B) connected with an input of an output module (190A, 190B) which is associated with the respective servomotor, whereby the associated servomotor is driven by a driving waveform according to a simulated result of the input of the output module. a main input shaft (151A, 151B) connected with the main shaft module to be driven according to the first driving waveform, an auxiliary input shaft (152A, 152B) connectable with the second drive module via a clutch module (170A, 170B) and capable, when disconnected, of rotating at the same phase as the first driving waveform or capable, when connected, of rotating according to said common driving pulse for providing a phase difference with respect to the first driving waveform, and an output shaft (153A, 153B) connected with an input of an output module (190A, 190B) which is associated with the respective servomotor, whereby the associated servomotor is driven by a driving waveform according to a simulated result of the input of the output module.