What is claimed is:1. A driving and resistance control system for driving a permanent-magnet synchronous motor or applying a resisting force to the permanent-magnet synchronous motor, the permanent-magnet synchronous motor comprising a stator and an external rotor, wherein the stator includes a plurality of stator windings, and the external rotor is provided with a plurality of permanent magnet units circumferentially arranged therearound, and the external rotor is combinable with a flywheel of an exercise equipment, comprising:a power supply circuit for supplying an electrical energy;a resistance generation device for generating a resisting force to the flywheel of the exercise equipment, the resistance generation device being provided with a discharge power element and a discharge resistor serially connected to the discharge power element;a control device, comprising:a processing unit;a motor driving circuit electrically connected with the power supply circuit and the plurality of stator windings of the permanent-magnet synchronous motor to drive the permanent-magnet synchronous motor;a resistance controller connected between the plurality of stator windings of the permanent-magnet synchronous motor and the resistance generation device, the resistance controller being provided with a first rectifier and filter and a PWM control circuit connected between the first rectifier and filter and the discharge power element of the resistance generation device; andan interlock control to the motor driving circuit and the PWM control circuit of the resistance controller;wherein in a first operation mode, under control of the interlock control of the control device, the processing unit generates a first PWM control signal to the PWM control circuit of the resistance controller to control the discharge power element, while disables sending of a second PWM control signal to the motor driving circuit, and under such an operation mode, the external rotor of the permanent-magnet synchronous motor is rotated by an operator applying a force to cause spinning of the flywheel, so that the permanent-magnet synchronous motor is operating in a generator mode to generate an AC generation voltage at the plurality of stator windings, wherein the generation voltage is fed to the resistance controller and converted into a DC voltage by means of the first rectifier and filter circuit, and then the DC voltage is applied through the discharge resistor to generate an enlarged current to thereby change a resisting force applied to the flywheel; andin a second operation mode, under control of the interlock control of the control device, the processing unit of the control device generates the second PWM control signal to the motor driving circuit to control the motor driving circuit, while disables sending of the first PWM control signal to the PWM control circuit 642, and under such an operation mode, the electrical energy is supplied from the power supply circuit, and the motor driving circuit supplies a driving current for the permanent-magnet synchronous motor under control of the second PWM control signal, so that the permanent-magnet synchronous motor is operating in a motor mode to generate an acceleration on the external rotor of the permanent-magnet synchronous motor.2. The driving and resistance control system according to claim 1, wherein the control device further comprises a hall sensor for detecting an angle of a rotating spindle of the permanent-magnet synchronous motor and generating a rotation signal supplied to the control device.3. The driving and resistance control system according to claim 1, wherein the control device further comprises a feedback circuit, and the feedback circuit comprises one of a current feedback circuit, a voltage feedback circuit, a Hall element, and a temperature element.4. The driving and resistance control system according to claim 1, wherein the exercise equipment is combined with a chassis, and the chassis is connected to a lifting device, and the processing unit is operable to control the lifting device so as to control a slope of the chassis to thereby control the exercise equipment for an uphill or downhill motion.5. The driving and resistance control system according to claim 1, wherein the stator of the permanent-magnet synchronous motor is further combined with a sensor support, and at least one stress sensor unit is mounted on the sensor support to measure torque-watt data of the operator applying a force to drive the flywheel.6. A driving and resistance control system for driving a permanent-magnet synchronous motor or applying a resisting force to the permanent-magnet synchronous motor, the permanent-magnet synchronous motor comprising a stator and an external rotor, wherein the stator includes a plurality of stator windings, and the external rotor is provided with a plurality of permanent magnet units circumferentially arranged therearound, and the external rotor is combinable with a flywheel of an exercise equipment, comprising:a power supply circuit for supplying an electrical energy;an electromagnetic resistance generation device arranged adjacent to the external rotor of the permanent-magnet synchronous motor; anda control device, comprising:a processing unit;a motor driving circuit electrically connected with the power supply circuit and the plurality of stator windings of the permanent-magnet synchronous motor to drive the permanent-magnet synchronous motor;a resistance controller connected between the plurality of stator windings of the permanent-magnet synchronous motor and the electromagnetic resistance generation device; andan interlock switch connected with the motor driving circuit, the permanent-magnet synchronous motor, and the resistance controller;wherein in a first operation mode, the interlock switch makes the motor driving circuit and the plurality of stator windings of the permanent-magnet synchronous motor open-circuiting, and makes the plurality of stator windings of the permanent-magnet synchronous motor connected to the resistance controller, and under such a condition, the external rotor of the permanent-magnet synchronous motor is caused to rotate by an operator applying a force to cause spinning of the flywheel, so that the permanent-magnet synchronous motor is operating in a generator mode to make the plurality of stator windings generate a generation voltage fed to the resistance controller, and the resistance controller changes an electromagnetic field intensity of the electromagnetic resistance generation device according to a pulse width modulation (PWM) control signal so as to change a magnitude of a resisting force acting on the flywheel; andin a second operation mode, the interlock switch makes the motor driving circuit and the plurality of stator windings of the permanent-magnet synchronous motor closed-circuiting, and cutting off control of the resistance controller, and the power supply circuit supplies electrical energy to the permanent-magnet synchronous motor through the motor driving circuit, so as to make the permanent-magnet synchronous motor operating in a motor mode to include an acceleration on the external rotor of the permanent-magnet synchronous motor.7. The driving and resistance control system according to claim 6, wherein the resistance controller comprises:a first rectifier and filter circuit connected to the plurality of stator windings of the permanent-magnet synchronous motor to filter and rectify the generation voltage into a DC voltage; anda PWM control circuit electrically connected with the first rectifier and filter and the electromagnetic resistance generation device, and is operable to generate, according to the DC voltage, the PWM control signal to control the electromagnetic field intensity of the electromagnetic resistance generation device, so as to generate an eddy-current resisting force on the external rotor during rotation of the external rotor to thereby change the resisting force acting on the flywheel.8. The driving and resistance control system according to claim 6, wherein the control device further comprises an angle detection unit for detecting an angle of a rotating spindle of the permanent-magnet synchronous motor and generates an angle signal supplied to the control device.9. The driving and resistance control system according to claim 6, wherein the control device further comprises a feedback circuit, and the feedback circuit comprises one of a current feedback circuit, a voltage feedback circuit, a Hall element, and a temperature element.10. The driving and resistance control system according to claim 6, wherein the resistance controller is further connected to a charging circuit to have the generation voltage that is generated by the plurality of stator windings of the permanent-magnet synchronous motor operating in the generator mode fed, after the first rectifier and filter circuit, through a charging circuit for backward charging into at least one energy storage device.11. The driving and resistance control system according to claim 6, wherein the electromagnetic resistance generation device comprises at least one electrical magnet, which is arranged on an outer circumference of the external rotor.12. The driving and resistance control system according to claim 6, wherein the power supply circuit comprises an alternate-current power supply, an energy storage device, or a combined power supply that includes an alternate-current power supply and an energy storage device.13. The driving and resistance control system according to claim 6, wherein the exercise equipment is combined with a chassis, and the chassis is connected to a lifting device, and the processing unit is operable to control the lifting device so as to control a slope of the chassis to thereby control the exercise equipment for an uphill or downhill motion.14. The driving and resistance control system according to claim 6, wherein the stator of the permanent-magnet synchronous motor is further combined with a sensor support, and at least one stress sensor unit is mounted on the sensor support to measure torque-watt data of the operator applying a force to drive the flywheel.15. A driving and resistance control system for driving a permanent-magnet synchronous motor or applying a resisting force to the permanent-magnet synchronous motor, the permanent-magnet synchronous motor comprising a stator and an external rotor, wherein the stator includes a plurality of stator windings, and the external rotor is provided with a plurality of permanent magnet units circumferentially arranged therearound, and the external rotor is combinable with a flywheel of an exercise equipment, comprising:an energy storage device;a resistance generation device for generating a resisting force to the flywheel of the exercise equipment;a control device, comprising:a processing unit;a motor driving circuit electrically connected with the energy storage device and the plurality of stator windings of the permanent-magnet synchronous motor to drive the permanent-magnet synchronous motor;a resistance controller connected between the plurality of stator windings of the permanent-magnet synchronous motor and the resistance generation device; andan interlock switch including a first switch and a second switch, the first switch being connected with the motor driving circuit and the plurality of stator windings of the permanent-magnet synchronous motor and the second switch being connected between the plurality of stator windings and the resistance controller;at least one electricity generation winding wound onto the stator; anda charging circuit connected to the at least one electricity generation winding through a second rectifier and filter circuit and connected to the plurality of stator windings through the resistance controller;wherein in a first operation mode, the interlock switch makes the motor driving circuit and the plurality of stator windings of the permanent-magnet synchronous motor open-circuiting, and makes the plurality of stator windings of the permanent-magnet synchronous motor connected to the resistance controller, and under such a condition, the external rotor of the permanent-magnet synchronous motor is caused to rotate by an operator applying a force to cause spinning of the flywheel, so that the permanent-magnet synchronous motor is operating in a generator mode to make the plurality of stator windings generate a generation voltage fed to the resistance controller, and the resistance controller controls the resistance generation device to generate the resisting force to the flywheel according to a pulse width modulation (PWM) control signal;wherein the generation voltage generated by the plurality of stator windings charges into the energy storage device through the resistance controller and the charging circuit during the first operation mode, and also a backward charging voltage generated by the at least one electricity generation winding charges into the energy storage device through the second rectifier and filter circuit and the charging circuit during the first operation mode;wherein in a second operation mode, the interlock switch makes the motor driving circuit and the plurality of stator windings of the permanent-magnet synchronous motor closed-circuiting, and cutting off control of the resistance controller, and an electrical energy stored in the energy storage device is supplied to the permanent-magnet synchronous motor through the motor driving circuit, so as to make the permanent-magnet synchronous motor operating in a motor mode to drive the external rotor of the permanent-magnet synchronous motor; andwherein a backward charging voltage generated by the at least one electricity generation winding charges into the energy storage device through the second rectifier and filter circuit and the charging circuit during the second operation mode.16. The driving and resistance control system according to claim 15, wherein the resistance controller comprises:a first rectifier and filter circuit connected to the plurality of stator windings of the permanent-magnet synchronous motor to filter and rectify the generation voltage into a DC voltage; anda PWM control circuit electrically connected with the first rectifier and filter and the resistance generation device, and is operable to generate, according to the DC voltage, the PWM control signal to control the resistance generation device to generate a resisting force to the flywheel.17. The driving and resistance control system according to claim 15, wherein the control device further comprises an angle detection unit for detecting an angle of a rotating spindle of the permanent-magnet synchronous motor and generates an angle signal supplied to the control device.18. The driving and resistance control system according to claim 15, wherein the control device further comprises a feedback circuit, and the feedback circuit comprises one of a current feedback circuit, a voltage feedback circuit, a Hall element, and a temperature element.19. The driving and resistance control system according to claim 15, wherein the exercise equipment is combined with a chassis, and the chassis is connected to a lifting device, and the processing unit is operable to control the lifting device so as to control a slope of the chassis to thereby control the exercise equipment for an uphill or downhill motion.20. The driving and resistance control system according to claim 15, wherein the stator of the permanent-magnet synchronous motor is further combined with a sensor support, and at least one stress sensor unit is mounted on the sensor support to measure torque-watt data of the operator applying a force to drive the flywheel.