Dynamometer

• US 4,327,578 A
• Filed: 12/19/1979
• Issued: 05/04/1982
• Est. Priority Date: 12/19/1979
• Status: Expired due to Term

• Current Assignee: Horiba Instruments Incorporated (Horiba Limited)
• Original Assignee: Horiba Instruments Incorporated (Horiba Limited)
• Inventors: D'Angelo, Severino
• Primary Examiner(s): Ruehl, Charles A.
• Application Number:
  US06/105,404
• Time in Patent Office: 867 Days
• Field of Search: 73/117, 73/133 R, 73/134, 73/861.18
• US Class Current: 73/116.06
• CPC Class Codes: G01M 17/0072 the wheels of the vehicle co-operating with rotatable rolls G01M17/022, G01M17/045, G01M17/065 take precedence

Abstract

A dynamometer system for simulating road load and vehicle inertia forces for testing vehicles in place. The system includes a DC motor power absorption unit (PAU) and a microcomputer based system controller for controlling both the road load and inertia forces simulated by the PAU. A non-declutchable flywheel is used to simulate mechanically a constant amount of inertia to minimize the power requirements of the PAU. The control scheme is designed to implement the classic dynamometer control expression (F=A+Bv+Cv² +I dv/dt) in a novel manner with a minimum amount of delay time. The microcomputer is provided with the following measured functions: speed, acceleration, and a torque signal. The total force output to be simulated by the PAU is determined by first calculating the actual force output of the vehicle, and then determining the percentage of the total force output that should be assigned to the PAU. In calculating the total force output of the vehicle, the inertia outside the torque loop is accurately accounted for, thus permitting the torque transducer to be placed adjacent the PAU. In addition, the force output control signal applied to the PAU is corrected by an inertia error function to insure that the actual inertia force simulated by the PAU corresponds to the desired inertia value. A novel method of accurately converting the frequency signal from the speed sensor to a parallel digital signal without introducing an excessive time delay is also disclosed.

Claims

1. In a dynamometer system for simulating road load and inertia forces for testing vehicles in place including at least one roller adapted for driving engagement with the driving wheels of a vehicle, a power absorption unit (PAU) coupled to said roller for simulating road load and inertia forces to which the vehicle would be subjected during normal operation, a torque transducer coupled to the roller and PAU assembly for producing a force signal, and a speed transducer coupled to the roller and PAU assembly for producing a speed signal;

the improvement comprising;

control means for controlling the total force output simulated by the PAU including,

first means for determining the total force output of the vehicle,

second means for determining the theoretical acceleration of the vehicle given its total force output and its current speed,

third means for determining the force to be simulated by said PAU so that the vehicle can achieve said theoretical acceleration and producing a force output control signal in accordance therewith, and

output means for controlling the force output of said PAU in accordance with said force output control signal.

2. The dynamometer system of claim 1 wherein said first means determines the total force output of the vehicle by adding to the force signal from said torque transducer the product of the inertia between the torque transducer and the driving wheels of the vehicle and the acceleration of said roller.

3. The dynamometer system of claim 1 further including fourth means for determining the actual inertia being simulated by said PAU, comparing said actual inertia with a preselected value and producing an error signal in accordance therewith, and modifying said force output control signal in accordance with said error signal.

4. In a dynamometer system for simulating road load and inertia forces for testing vehicles in place including at least one roller adapted for driving engagement with the driving wheels of a vehicle having associated therewith a given inertia value (I_T), a flywheel coupled to said roller for mechanically simulating at least a portion of the total inertia (I_T) associated with the vehicle, a power absorption unit (PAU) coupled to the roller and flywheel for simulating both road load forces and the balance of the total inertia (I_T) not simulated mechanically, and a torque transducer and a speed transducer coupled to the roller, flywheel and PAU assembly for producing a force signal and a speed signal respectively;

the improvement comprising;

control means for producing a force output control signal for controlling the total force output simulated by the PAU, including error compensation means for determining the actual loop inertia being simulated on the PAU side of the torque transducer, comparing it with a preselected loop inertia value, and modifying said force output control signal in accordance with the result of the comparison.

5. The dynanometer system of claim 4 wherein said error compensation means determines the actual loop inertia being simulated in accordance with the force signal from said torque sensor and the speed signal from said speed sensor.

6. The dynamometer system of claim 4 wherein said preselected loop inertia value is established in accordance with the weight of the vehicle and the mechanical inertia associated with the components in said assembly outside of the torque loop.

7. In a dynamometer system for testing vehicles in place including a power absorption unit (PAU) for simulating road load and inertia forces and control means for producing a force output control signal for controlling the total force output being simulated by said PAU;

the improvement comprising means for comparing the actual inertia being simulated with a preselected inertia value and modifying said force output control signal in accordance with the difference therebetween.

8. In a dynamometer system for simulating road load and inertia forces for testing vehicles in place including at least one roller adapted for driving engagement with the driving wheels of a vehicle, a power absorption unit (PAU) coupled to said roller for simulating road load and inertia forces to which the vehicle would be subjected during normal operation, a torque transducer coupled to the roller and PAU assembly for producing a force signal (F_t), and a speed transducer coupled to the roller and PAU assembly for producing a speed signal (V);

the improvement comprising;

control means for controlling the total force output simulated by the PAU including means for determining the total force output (F) of the vehicle by adding to said force signal (F_t) the product of the mechanical inertia (I_r) of the dynamometer system between the torque transducer and the driving wheels of the vehicle and the acceleration (dv/dt) of the roller and means for determining the force to be simulated by said PAU in accordance with the total force output (F) of the vehicle and said speed signal and producing a force output control signal in accordance therewith, and output means for controlling the force output of said PAU in accordance with said force output control signal.

9. The dynamometer system of claim 8 wherein said control means further includes means for comparing the actual inertia being simulated with a preselected inertia value and modifying said force output control signal in accordance with the difference therebetween.

10. In a dynamometer system for simulating road load and inertia forces for testing vehicles in place including at least one roller adapted for driving engagement with the driving wheels of a vehicle, a power absorption unit (PAU) coupled with said roller for simulating road load and inertia forces, a torque transducer coupled to the roller and PAU assembly for producing a force signal (F_t) and a speed transducer for producing a speed signal (V);

the method of controlling the force simulated by the PAU including the steps of;

determining the total force output (F) of the vehicle by adding to said force signal the product of the acceleration (dv/dt) of the roller and the mechanical inertia (I_r) of the dynamometer system between the torque transducer and the driving wheels of the vehicle,

determining the force to be simulated by said PAU in accordance with the total force output (F) of the vehicle and said speed signal and producing a force output control signal in accordance therewith, and

controlling the force output of said PAU in accordance with said force output control signal.

11. The method of claim 10 further including the steps of comparing the actual inertia being simulated with a preselected inertia value and modifying said force output control signal in accordance with the difference therebetween.

12. In a dynamometer system for testing vehicles in place including a power absorption unit (PAU) for simulating road load and inertia forces and control means for producing a force output control signal for controlling the total force output simulated by said PAU;

the method of regulating said force output control signal including the steps of;

determining the actual inertia being simulated;

comparing said actual inertia with a preselected desired inertia value and producing an error signal proportional to the difference therebetween, and

modifying said force output control signal in accordance with said error signal.

13. In a dynamometer system for testing vehicles in place including a power absorption unit (PAU), a speed transducer for producing a frequency speed signal, and control means for controlling the force output simulated by said PAU in accordance with said speed signal;

the improvement comprising conversion means for converting said frequency speed signal to a digital speed signal including;

counting means connected to receive said frequency speed signal for counting the number of speed pulses received within a predetermined time period plus the first speed pulse received after said predetermined time period and producing an output signal representative of the total count, and

timing means for timing said predetermined time period plus the additional elapsed time until receipt by said counting means of said first speed pulse and producing an output signal in accordance with the total elapsed time period.

14. In a dynamometer system for testing vehicles in place including a power absorption unit (PAU), a speed transducer for producing a frequency speed signal, and control means for controlling the force output simulated by said PAU in accordance with said speed signal;

the method of converting said frequency speed signal to a digital speed signal including the steps of;

counting the number of speed pulses received within a predetermined time period plus the first speed pulse received after said predetermined time period and producing an output signal representative of the total count, and

timing said predetermined time period plus the additional elapsed time until the appearance of said first speed pulse and producing an output signal in accordance with the total elapsed time period.